If its happening at stock then it could be what phatboy said.. there is a string in Registry Computer/HKEY_LOCAL_MACHINE/SYSTEM/currentControlSet/control/session manager/MemoryManagement called SessionPoolSize and its at 4 by default. You can try 20 its also for gui and gpu parts of the driver. I use this for a long time and didnt saw any problems yet. There is another value SessionViewSize at 48 by default, but at 60 there were some side effects like slower aero or unusual game loading, better leave that at default 48. About that sleep issue, do you use logitech keyboard and LGPS 8.20sw? edit: or downgrade to 285.79/290.53?