This issue concerns Firefox and some odd behavior with one forum that I belong to. The issue only occurs at this forum, it does not happen at any other forum or web site. What happens is this:
I open Firefox, and, as I have been doing for almost two years, I try to go to the forum. I receive a 404 error message. I shut down Firefox, then restart it. Sometimes, on the second attempt, the forum portal will open, sometimes it will take me three or four attempts before I can get past that front page. Then, as I try to navigate around the site, I'll continually get 404 messages, requiring me to restart Firefox again.
Initially, I thought that there was probably some bug at the forum. Then, quite by accident, I stumbled on an odd thing - if I have two instances of Firefox open, I have no problem whatsoever entering or navigating around the forum. As soon as I close the instance of Firefox that is not logged on to the forum, the behavior starts up again.
Out of curiosity, because I still have Win XP installed on another drive, I tried going to the forum under XP. Absolutely no problems at all. So, thinking that perhaps I might have a bad installation of Firefox on the Win 7 drive, I uninstalled it, redownloaded the installer, and reinstalled Firefox. The same thing. I have to have two instances of Firefox open in order to have this particular site function normally under Win 7.
In terms of operating systems, applications, etc., I am a n00b when it comes to Win 7. However, I've been playing with computers for almost twenty years, and I like to think that I have a fair level of competence. This is something that I have never, ever seen before. For the life of me, I cannot figure out what the issue could be here.
I've hesitated to even post this here, because I've been a little afraid that you all might think I'm a completely bat-poop crazy little b*tch. But I swear, this is not something I'm making up, nor is it a delusion...

Any help or thoughts on this?