Kinda like Browsers force-closing on an Android Smartphone, huh?
Does Windows report any errors when these Browsers crash? OR are there any Errors reported in the Application Event Log? If so, what is the exact text?
http://social.technet.microsoft.com/Forums/en-US/w7itproperf/thread/6dc192ef-44f9-469e-a961-32674f7a... discusses how insufficient disk space, Adobe Flash (or other Add-on) issues, corrupt Windows system files, or even the video driver could cause such a problem.
I'd also throw in Disk errors as another possibility and would check the System Event Log for any such reports and run CHKDSK C: /F /R from an elevated Command Prompt (right-click on the Command Prompt icon and choose "Run as administrator" from the popup menu).
Deleting the Browser cache or even resetting to default settings is another troubleshooting step for Browser issues.
Another thing to check is if your wife reboots the laptop regularly. It's the only way to recover leaked memory lost by improperly-coded drivers and applications. If Sleep or Hibernate is always used to shut down the system, the leaked memory is never recovered and will accumulate until it causes a problem (same thing with the Android OS) . So one of the first troubleshooting steps should always be to reboot the system and see if the issue persists.
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT