Strange scrolling behavior in IE with checkboxes in a scrollable div

I have a "multiselect" control that looks like this (sorry for the long id names, they are kinda autogenerated because this whole thing is being generated by a custom tag):

<div class="default-skin-outer" id="myMapSelect_multiSelectOuterDiv">
    <div class="default-control" id="myMapSelect_multiSelectControlDiv">
        <span class="default-icon-check-text" id="myMapSelect_multiSelectControlCheckWrapperSpan">
            <span class="default-icon default-icon-check" id="myMapSelect_multiSelectControlCheckIconSpan"></span><span class="default-icon default-icon-text" id="myMapSelect_multiSelectControlCheckTextSpan">Check All</span>
        </span>
        <span class="default-icon-uncheck-text" id="myMapSelect_multiSelectControlUncheckWrapperSpan">
            <span class="default-icon default-icon-uncheck" id="myMapSelect_multiSelectControlUncheckIconSpan"></span><span class="default-icon default-icon-text" id="myMapSelect_multiSelectControlUncheckTextSpan">Uncheck All</span>
        </span>
    </div>
    <div class="default-skin-inner" id="myMapSelect_multiSelectInnerDiv">
            <ul class="default-multiselect">
                        <li class="default-multiselect">
                            <label class="default-label">
                                <input type="checkbox" value="0" class="default-checkbox" id="myMapSelect0" name="myMapSelect"> Zero
                            </label>
                        </li>
                        <li class="default-multiselect">
                            <label class="default-label">
                                <input type="checkbox" value="1" class="default-checkbox" id="myMapSelect1" name="myMapSelect"> One
                            </label>
                        </li>
                        <li class="default-multiselect">
                            <label class="default-label">
                                <input type="checkbox" value="2" class="default-checkbox" id="myMapSelect2" name="myMapSelect"> Two
                            </label>
                        </li>
                        <li class="default-multiselect">
                            <label class="default-label">
                                <input type="checkbox" value="3" class="default-checkbox" id="myMapSelect3" name="myMapSelect"> Three
                            </label>
                        </li>
                        <li class="default-multiselect">
                            <label class="default-label">
                                <input type="checkbox" value="4" class="default-checkbox" id="myMapSelect4" name="myMapSelect"> Four
                            </label>
                        </li>
                        <li class="default-multiselect">
                            <label class="default-label">
                                <input type="checkbox" value="5" class="default-checkbox" id="myMapSelect5" name="myMapSelect"> Five
                            </label>
                        </li>
                        <li class="default-multiselect">
                            <label class="default-label">
                                <input type="checkbox" value="6" class="default-checkbox" id="myMapSelect6" name="myMapSelect"> Six
                            </label>
                        </li>
                        <li class="default-multiselect">
                            <label class="default-label">
                                <input type="checkbox" value="7" class="default-checkbox" id="myMapSelect7" name="myMapSelect"> Seven
                            </label>
                        </li>
            </ul>
    </div>
</div>

The CSS for this whole thing is:

div.default-skin-outer {
    -moz-border-radius: 5px;
    -webkit-border-radius: 5px;
    width: 300px;
    height: auto;
    padding: 2px;
    background-color: #f0f0f0;
    border: 1px solid #999999;
}

div.default-skin-inner {
    overflow: auto;
    width: 300px;
    height: 100px;
}

div.default-control {
    -moz-border-radius: 5px;
    -webkit-border-radius: 5px;
    width: auto;
    border: 1px solid #555555;
    background-color: #999999;
    color: #f0f0f0;
    vertical-align: middle;
    padding: 2px;
    margin-bottom: 2px;
    font-weight: bold;
    overflow: hidden;
}

ul.default-multiselect {
    padding: 0px;
    margin: 0px;
    white-space: nowrap;
}

ul.default-with-padding {
    padding: 0px;
    padding-left: 20px;
    margin: 0px;
    white-space: nowrap;
}

li.default-multiselect {
    list-style-type: none;
}

label.default-label {
    display: block;
    padding: 2px;
}

input.default-checkbox {
    width: 13px;
    height: 13px;
    padding: 0;
    margin: 0;
    vertical-align: bottom;
    position: relative;
    top: -1px;
    *overflow: hidden;
}

span.default-icon {
    background-image: url("/resources/authoring/jqueryui/custom-theme/images/ui-icons_ffffff_256x240.png");
    display: inline-block;
    height: 16px;
    width: 16px;
    overflow: hidden;
}

span.default-icon-text {
    开发者_开发百科width: auto;
    background: none;
}

span.default-icon-text:hover {
    text-decoration: underline;
    cursor: pointer;
}

span.default-icon-check-text {
    float: left;
}

span.default-icon-uncheck-text {
    float: right;
}

span.default-icon-check {
    background-position: -64px -144px;
}

span.default-icon-uncheck {
    background-position: -96px -128px;
}

This works beautifully in Firefox. The checkboxes scroll without any problem in the scrollable div. But when I looked at this in IE8, it looks terrible.

Firstly, the extra checkboxes bleed outside the main div. Secondly (and this is the really strange thing) when I use the scroll bar, the text scrolls, but the checkboxes do not. They simply stay in place while the text scrolls. I tried googling for a solution but was unable to come up with anything.

Thanks!

UPDATE

So I found out that if I remove the funky part in the checkbox styling:

vertical-align:bottom; 
position:relative; 
top: -1px; 
*overflow: hidden; 

It works fine. But I put that in to make sure my labels and checkboxes are lined up properly.

Oh yes as far as the compatibility view is concerned, this is IE8 running under compatibility mode.

In response to the comments about inherited styles, here are styles that the checkbox inherits:

input {
   border:1px solid #CFCFCF;
   color:#000000;
   font-family:Arial,Verdana,Sans-Serif;
   font-size:12px;
   padding-left:4px;
}


li.default-multiselect {
   list-style-type:none;
}

ul.default-with-padding {
   white-space:nowrap;
}

table {
   empty-cells:show;
}

html, body {
   line-height:16px;
}

I don't see anything that could potentially interfere...

There seems to be some strange interaction between inherited styles and the styles I have defined. That much is clear from Jacob's and Ray's comments since they were able to slap this code onto a page and have it render fine in IE without any issues.

I was able to make it behave properly by removing position:relative from the input.default-checkbox style.

I'm assuming that some sort of bizarre interaction is making the checkboxes think they are positioned statically or absolutely (or something) due to which they don't scroll. At least I think that's the reason; someone may be able to provide a better reason and shed light on this. At any rate, by removing the position:relative, I was able to make the strange scrolling-behavior stop. Thanks for helping me figure this out!

As @rossisdead suggested, adding position: relative to the scrolling element solves the problem. I also had to add position: relative to the parent of the scrolling element.

Make sure you don't have position: fixed set on your checkboxes in any other stylesheets.