Is this a factory overclocked GT8800?
From the lotro forums
Black screen issue with "Factory Overclocked" cards
"Black Screen" while playing with a "Factory Overclocked" Nvidia card
Black screen issue with "Factory Overclocked" Nvidia graphics cards
There is a very specific crash situation that occurs with some models of "Factory Overclocked" graphics cards in Lotro and other games:
* The game enters a "black screen" but the sounds etc still are playing
* Alt-tabbing or otherwise changing the games focus causes the crash
This is an issue related to the Factory Overclocking settigns of the cards, known fixes or workarounds are:
* Lowering the games "Engine Speed" and/"Graphics Quality" settings mitigates/eliminates this
* Reducing the overclocked card back to "stock" speeds mitigates/eliminates this
* Replacing the failing card eliminates this
The card is entering a fault state due to heat/voltage and attempting to reset but fails and causes a crash, reducing the "stress" that the game places on the card can mitigate or outright eliminate occurances of this.