re: Firefox 1.5 - WTF?
I uninstalled Firefox 1.0.7 on my PC and my nephew's box (my former box), restarted, then installed Firefox 1.5. I have not seen any problems other than the Firefox 1.5 setup on my PC informing me that the Qute 3 theme is not supported. The latest version, 3.0.1, works with Firefox 1.5. I am also running the latest Macromedia Flash and Sun Microsystems Java.
Are you running Firefox with a bunch of extensions, themes, and toolbars? Could a firewall be blocking the new browser?