I typically use NoScript in conjunction with Firefox to block out any lurking digital nasties - I've found myself having to remove rather a lot of them from clients' machines at work. But when I patched to Firefox 4 (and later 5), all my Google Custom Search links no longer worked. In IE8 & 9 it was still OK.
Then everything worked just fine again, after I updated an older version of NoScript to the most recent (v2.1.2rc3). Each successive version of Firefox seems to shift the goalposts for add-on developers.