Just edited somthing I just said on a mozilla forum, but:

God knows why this has happened, but basically, Firefox no longer opens at all. The process begins to open then the memory will peak at around 18-20,000k and then the CPU % will drop to 0 and it'll just drop to around 3,000k and hang until I kill the Firefox process.

With regards to Spybot, it'll openand ask me if I'd like to clear my temp folder as per usual, but after this, it will not progress any further.

It all started about an hour ago when Firefox suddenly crashed when I tried to open some random link. Tried to reopen it immediately after it crashed and nothing happened. So I restarted my PC. FF still wouldn't open. So I gave Safe Mode a go, disabled everything, but after that menu, the same problem occured again. Firefox just wouldn't open.

So I thought that maybe my profile may have been corrupt, so I made a new one and set FF to allow me to choose a profile when it opens. Choosing the new profile, even in Safe Mode still leads to the same problem of it reaching around 18-20,000k before the CPU gives up and drops it to 0%.

I thought maybe it was something to do with Java, so I uninstalled that from my PC and reinstalled it via Opera. Opera is a bit annoying though since it doesn't open every web page, so I've had to resort to IE for now.

For what it's worth, Spybot S&D no longer opens either and follows the same problem, so whatever the root cause for FF not opening may be related to something it shares with Spybot?

Not a clue what's going on here, but it's really annoying.