Problem uploading .docx through html form

I've made a simple form, with the proper enctype for uploading files. When i try to upload a .docx everything works fine in IE 8 and Safari, but in Firefox or IE 7开发者_运维技巧 or 6 i can't even click submit, nothing happens! Could this still be a server issue? It's an apache server.

Everything works fine if i choose to upload a .doc file

<form enctype="multipart/form-data" method="post" action="index.php">
    <input name="file" type="file" />
    <input type="submit" name="btnSubmit"  value="Submit"/>
</form>

I tested your form in my Wamp2.0 with IE7 and Firefox,and it works fine.I don't think it could be the server issue since the form works well in you IE8.Perhaps you should standardize your html code,or check you browsers.