Useful thread where I got my solution

The Gingerbreadman on in that link seems he knows his stuff.

I had the same problem and most of Mozilla's answers on here were so useless.

Anyway - I think your problem is likely to be the Add-On 'Silverlight' - disable it and see if you can then select the attachments link.

Tools>Add Ons>Plugins> Disable Silverlight :)

You guys are not going to believe this I figured out the problem it's really dumb...ok here goes the attachment uploader loads seperate so I got to thinking it's a popup so I went to options content and under block pop ups there is an option exceptions click on that and in the box type firefox.com and hit allow pow its fixed!!!!! :-)

You don't have to disable any addons or extentions!!!You guys are not going to believe this I figured out the problem it's really dumb...ok here goes the attachment uploader loads seperate so I got to thinking it's a popup so I went to options content and under block pop ups there is an option exceptions click on that and in the box type firefox.com and hit allow pow its fixed!!!!! :-)