1) My computer won't go to sleep.
2)I get a black screen with audio when i play games full screen.
I recently installed a second GTX 260 to my system. I now run two GTX 260s in SLI. Before SLI, I had no problems like I mentioned above.
My first problem is extremely annoying. I cannot put my computer into sleep mode. When I click "sleep", the monitor goes off instantly as always, the computer then takes about five seconds, which is usual, then it makes the sound it always does when it goes to sleep (a click), however instead of shutting down after the click, nothing happens, the LEDs don't even turn off for a second. The only thing that does happen is that my 260s fan speed goes to 100% as if the PC were booting. I have no display signal after this and must force a shutdown manually with the power button. When I restart, the PC boots and acts as if it were a cold start, however my previous session is still available, as if it just awoke from sleep. I am currently using the 186.18 driver from nVidia and have also tried the newest and older drivers to no avail.
My second problem has to do with full screen gaming. When I play crysis for example (happens with all games), I can hear the opening credits and later the menu screen, however, there is a black display. I am getting a signal, however it is pure black. I can get the game to work properly in windowed mode all of the time. I also can get full screen to work if i unplug the cable (RGB w/ DVI adapter) from the card, then plug it back in. This is an annoying process that i should not have to go through in order to play a full screen game.
Have you checked your drivers? And you may possibly need configure your audio again via the control panel. I personally dont have a gtx 260 but i do know they have been having problems with audio.Reinstall your audio and video drivers. Also try swapping the 2 cards places?