I have this problem and have had it for some time (I think since I first went to Firefox 4 on Win XP). I'm now on Firefox 6 on Win 7 Professional.
The problem is the same for all platforms. I have numerous rss feeds on my iGoogle page. *Sometimes* when iGoogle loads, all (or most) of the text labels in the headers of the feeds are not "clickable". They just have the "cross" mouse cursor for moving the feed box. But *sometimes* they all (or most) work just fine. If I load the page and no headers are clickable, then I usually hit F5 a few times and they finally start working. When they're not working, the only way to click through to the blog (or whatever each feed is for), is to click on one of the individual articles in the feed box and then hit the "Home" button (or whatever) once I get to the website.