I've been on a brand new build and after a few weeks it turned out my Seasonic X660 PSU seemed to be going bad on a handful occasions (cursor freezes, sudden restarts, ...; got the GigaByte boot loops as well).
I'm sure one or all these instances had Firefox 15 opened, but I don't feel it was the cause. But IMO, one of the freezes or restarts damaged something that FF needs.
I'm back up now with my older PSU. Firefox still starts up instantly but is loading pages slower than an old phone modem, if at all [currently fresh install, no extensions]
I first followed all the regular tips, then reinstalled, the 2nd time trying to delete everything I could find from Mozilla first, but it keeps on doing it... IE 9 is fine.
I did an "sfc /scannow" and "check disk" with no problems found. Also explicitly letting it through Windows firewall. So I'm figuring Mozilla is using some part of Windows that IE doesn't need and may be damaged?
I feel lost without Firefox and ran it very fast and perfectly with 25 extensions...
Any clue? Would I have a better chance with an older version that maybe didn't use certain technology yet? (haven't asked in the Mozilla forums yet, cause I'm considering you guys smarter
If this could be found, it might be the cause for other users too.