Search button seems to be fine, but I guess that's because I'm not logged in. Post here your navbar and header templates.
Two errors that I did notice:
1. I see one </if> in html source, so looks like you forgot <if> somewhere or made error in code.
2. You have invalid meta tags in header:
Code:
<META http -equiv=Page-Exit content=BlendTrans(Duration=0)>
<META http-equiv=Page-Enter content=BlendTrans(Duration=0)>
Besides space problem on first line, those <META> should be <meta> (in lower case) because you are using xhtml, not html. My guess is that you have similar problem with search - some html code is in upper case while it should be in lower case and firefox doesn't tolerate such errors.