I have had this problem with my Dell Laptop starting 6 months after purchase. They have replaced the harddrive twice, the memory and the monitor. I'm pretty sure it is a driver
or Windows 7 update issue. The computer worked fine until I tried to update drivers
, but also updated windows on the same day. 3 times my laptop has been sent to Dell Depot for repairs and each time I reload windows and try to install drivers I have the same issue. I followed one trouble shooting suggestion in tutorials and found that although I have hibernate (3) I don't have sleep (2) installed in bios.