Hardy freezes with Firefox Dell X200

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Fresh install of Hardy. Firefox 3.0b5 all Ubuntu updates.
Dell X200 Laptop. 512 ram, latest BIOS
I am trying to get Hardy to be stable to take this small laptop on a 
trip but at this point it is unreliable.
The laptop freezes. The screen is there but the mouse pointer frozen and 
the only button that works is the off switch.
It seems to happen only when Firefox is running. I left it on all night 
with Thunderbird running and had no problems
this morning. When I started using Firefox the problem came back. Once 
while searching a website in Firefox, once
while trying to add a printer. Once while trying to print from Firefox. 
Each time required a restart.
  Other than being a little slow, 800mhz, it seems to be working fine 
until it locks up.
I just installed Opera and have been using it for about an hour with no 
lockup but would prefer Firefox.

Where do I start?
Thanks,
Bradley