Did the same to me. Weird. Apparently, you have to fake it with ASCII codes: about:config.
YAY! I just reset everthing to default, and now it works like I want( after I went back along the path I mentioned earlier and set foreign links to open in a new tab ) Thanks!
Another Firefox user checking in. I tried it when it was still Phoenix and thought it a little cludgey. Since late .8 it’s been a fairly solid product, and I love it.
Although if you’re wanting an IE engine with a Firefox(ish) feel (i.e. tabbed browsing, mouse gestures etc. try MyIE2, recently renamed Maxthon because the release of version 1 was imminent. http://www.maxthon.com/en/index.htm ). I used this for a long time before I started using Firefox. 0.9.3 is also very stable with Google’s Gmail.
Adblock is a must have extension IMO.
FTR, I also use Mozilla’s Thunderbird. Fast, efficient, full featured and not Outlook. 
As a direct result of this thread and the Firefox extensions thread, I’ve downloaded and installed Firefox. I’ve been using it for a day and a half (or so) and am quite pleased. I can see why y’all like it so much. I’d never even heard of it before this. I’m a little disgruntled with how poorly it handles Flash and PDF so far. Both seem to make my whole system hang. I don’t like hanging. Unless I’m on the jungle-gym. Which I’m not.
Oh, and did I mention that it seems to start up a wee bit slower and load web pages a bit more than a wee bit (but not by much) slower.