switching accounts

my wife and i have seperate email accounts and the only way to access these is for her to switch from my account (which is always on) to hers to check it. the problem is when she switches the screen goes blank and nothing! i need to reboot to get back in again and the it behaves normally. whats going on?

maed her a thunerbird email account on my user account so no need to change now, still dont know what the problems was though?

Perform a clean boot and try,

Also update your display driver.

thank you delphin, ill try that:D