You'll probably need to dump your profile folder - something that was a common requirement in pre 1.0 upgrades. This page might be helpful.

Do a spyware scan and uninstall that beloved Comet Cursor of yours and it should be fine. I've never had an issue with Firefox besides the irritatingly slow download window delay.
Oh, and get rid of your plugins.

Spyware? Comet Cursor? O_o

I've tried everything but simply yanking Firefox entirely, testing for a day or two, and then re-installing. But I just can't see myself going without FF for that long.

I've yanked the plugins. I've killed the profiles, and the folder. (Which kills the plugins anyway.)

Oddly enough, after crashing 3-20 times a day for the past week, it's been well behaved since I posted this, with no changes or fix attempts. I think it's on to me, whatever it is. I'm just waiting for my browser to start talking to me. "Dave... I'm sorry, I cannot do that Dave. MetaChat is a bad influence on you... It makes you drink, Dave."

This may or may not be related to your issue but it is good to know:

Fix a memory leak in Firefox 1.0

Thanks, mlis, and everyone else. I think that memory leak fix is exactly what I needed. I'm now using a fresh FF install with a manually wiped application data/profile folder and with the memory cache patched in user.js. I'm about to start slowly re-adding my extensions and plugins and keeping track of them just in case it was one of those.

This has seriously been a pain in the ass. I keep having to reboot from hard freezes 5-30 times a day or something. Fuckin' ridiculous.

Crap, that wasn't it either. I haven't been this frustrated with one of my own (generally nicely configured) machines in a long, long time. I actually caught myself pounding ctrl-alt-delete and smacking my mouse around, and even entertaining those thoughts that go something like: "Bitchy computer? Oh, fuck no! Oh, look, there's a window right here. Reach beneath the desk, grab the CPU case and chuck that cocksucking motherfucker out the window! Comon'! It'll be fun! Y'know you want to!"

After reading more of the links provided here, and links found from these links it's just looking like FF 1.0.6 just has a completely insane set of difficult-to-reproduce issues. I've wiped the profile folders, application data folders, program folders, registry entries and killed all extensions and plugins, including everything macromedia on my machine and rolled back to FF 1.00. Fer fuck's sake, 0.86 runs more stable on my P1 266 mhz laptop with 48 megs of ram and a totally encrusted Win98 install.

So far so good.

There's a slim chance that a memory stick went bad or something, which I'll discover shortly if so, but I highly doubt that's it - 'cause if I turn everything FF related off and just don't load or touch it, it works fine, and I throw some really heavy apps at this old desktop machine, like Traktor, Reason, Photoshop, Wavelab, CorelDraw and more.