Currently Being ModeratedFeb 2, 2012 7:02 PM (in response to David Illig)
Some things to consider.
Create another admin account and see if the same thing happens in that user account. If not, then you have a problem in the primary user account.
I am assuming you zapped PRAM and did an SMC reset, plus unplugged all periphals for awhile.
If the machine recently started acting this way, look at recent installs. If it has acted like this since you installed 10.7.2 you might reinstall using the combo update or install the 10.7.3 combo update.
You can also reinstall Lion and not lose your data.