Then fix your installation.
You either have junk installed into Firefox that's making it unstable, or your OS build is inherently unstable.
There is absolutely nothing wrong whatsoever with Firefox on Vista x64.
Which addons do you have installed?
Those are plugins. What's being asked for are what extensions you have installed. While you're at it, you haven't even given the Fx version you have installed.
When it crashed, did you get the crash reporter? Did you submit the report? If yes to both of those, it should be listed in about:crashes.
How do you make it crash? Does it still do it in safe mode or with a new profile.
If you google, you'll find lots of "potential conflicts/issues" with anything at all. There is not an inherent issue with using Fx on a 64-bit OS.
Type about:crashes into the address bar...
Signature SkypeFfComponent.dll@0x440c3
UUID 9f7d25d8-c769-40dc-8c84-dd0022100903
Time 2010-09-03 11:26:46.955901
Uptime 3
Last Crash 1074 seconds (17.9 minutes) before submission
Install Age 3554437 seconds (5.9 weeks) since version was first installed.
Product Firefox
Version 3.6.8
Build ID 20100722155716
Branch 1.9.2
OS Windows NT
OS Version 6.0.6002 Service Pack 2
CPU x86
CPU Info GenuineIntel family 6 model 15 stepping 11
Crash Reason EXCEPTION_ACCESS_VIOLATION
Crash Address 0x828c070
User Comments
Processor Notes
EMCheckCompatibility False