I use the proxy autoconfigure script at http://david.woodhou.se/proxy.pac.txt to provide access to company-internal web sites, and to things which are problematic from within China. I noticed yesterday that the dnsDomainIs() tests don't seem to be working -- it always falls through to the 'DIRECT' at the end. I can make things work by uncommenting the unconditional proxy line (yes, I know that one's a different port). This used to work fine, until quite recently. I installed firefox-2.0.0.5.1.fc7 on the 18th of July; it's probably been broken since then. I don't think I've done anything in the last couple of weeks which would cause me to notice the breakage -- I rarely access company-internal web pages, and I haven't actually been in China until yesterday, so direct access to the BBC and Wikipedia would have worked fine.
And this code has not changed since 2001, not sure why it's suddenly failing. function dnsDomainIs(host, domain) { return (host.length >= domain.length && host.substring(host.length - domain.length) == domain); } I suppose you can try including that function yourself, in the pac file to see if it helps. Otherwise, perhaps the breakage is that host is not getting set properly? alert() might help debug there.
Ah, this hotel seems to have started giving DNS results for nonexistent hosts -- so removing the 'isResolvable()' test for redhat-internal makes it work. Sorry for the noise.