Users having problems clicking submit button

I have a few users testing a site of mine which has 2 text fields and an image for a submit button. I can't replicate the problem on my side, nor can I seem to find anyone else that is having it either. The problem is that the submit button doesn't do anything when they click it. When I click, and the fields are empty or invalid, I get a JS alert, and can click it as many times as I want and it works just fine. One of the users can click it with the same result, but only once, then he has to refresh the page. The other can't click it at all, the cursor doesn't even change to indicate he's hovering over anything.

This is the code for that table cell and the button开发者_开发问答.

<td>
    <img src="images/1x1clear.gif" alt="" width="3" height="99">
    <input type="image" src="images/1x1clear.gif" name="submit" value="submit" width="180" height="53" border="0">
</td>

Does anyone have an idea why this could cause problems? Could it just be problems with their computers or browsers?

Thanks

EDIT

We're using JQuery the form is submitted by using something like

form.submit(function(){ alert("clicked"); }

One of the comments in the docs for form.submit() on the jquery website says this:

A word of advice... if you have a submit button in your form (), and the NAME or ID of the button is also "submit"... this function may fail. I wasn't getting an error message or anything... just... silence. It was eerie. =)

Try changing the name attribute of the button to something other than "submit".

<td>
    <img src="images/1x1clear.gif" alt="" width="3" height="99">
    <input type="image" src="images/1x1clear.gif" name="somethingotherthansubmit" value="submit" width="180" height="53" border="0">
</td>

I don't know if this will fix your problem, but you could use a <button> instead of an <intput type="image" />. I've found that this is far more reliable as it works in a similar fashion as <input type="submit" />.

<td>
    <button type="submit" name="submit">
        <img src="images/1x1clear.gif" alt="" width="3" height="99">
        <img src="images/1x1clear.gif" width="180" height="53" border="0">
    </button>
</td>

Then you can determine if you need both the images or not.

Use CSS and use a regular button:

.btnSubmit {
   width:180px;
   height:53px;
   background-image:url(images/1x1clear.gif)
}

<input class="btnSubmit" type="submit" name="submit" >