I found a solution
download
Process Explorer Copyright © 1996-2010 Mark Russinovich Sysinternals - www.sysinternals.com
and suspend in the background tast per task , play with what you suspend and start the tasks again ,and your SL work cool and smooth again.
also consider to run to run
Instant Memory Cleaner from http://www.vasileios.gr/freesoft
For me it works great enjoy
Tomorow i will explain how i donne it: it has nothing todo whit a bug or graphics card, its only a issue with the memory you use and whats eating it up by background tasks... I mean with the default taskmanager its almost impossible to see
whats running in the background of your computer, or more difficult to kill or suspend a task. Enjoy !!!