System breakdown after entering SL main land

I'm taking a wild shot here: Yesterday I entered the main land in SL after I have trained on Orientation Island and Help Island. Amongst others, I experienced being catapulted into another sim, without anyone having kicked me or shot firearms at me.
Today I stood in a building and whenever I turned around, massive pixelation would occur, and finally the SL screen would be all red, or half green, after which my monitor turned itself off.

When I restarted my computer after the last, it would either turn itself on and off, or it would turn only the screen off, and let the radio play on. The only working solution I found, was to rebuild the system from a system point from before I installed SL.

Does anyone have an idea, what this was about?

Sounds as if your graphics card is less powerful than your preference settings would suggest. (Search these forums for tips on your specific graphics card.)

Here are some general tips:

Add as much Real Physical RAM as you can to your PC
Make the Cache HUGE
Set the DRAW distance to 64
Turn OFF: (local lights, ripples, shiny, etc.)

Thank you, will try that