Fixing someone's Vista computer. Process: I click any program or process that opens a User Account Control prompt. Screen goes dim so you may hit Continue to perform a secure user action. I click Continue Screen goes black for 30 seconds to 1 minute while you wait for the screen to return. In another example I click Cancel and screen still then goes black for 30 seconds to a minute. In that timeframe a chime goes off while you wait. (No chime if it was being cancelled.) Then screen comes back to continue with whatever. Something is occurring after the UAC prompt. Considering everything is practically a UAC acceptance this can get pretty annoying pretty quickly. Laptop has external monitor to regular external plug. Works fine. Laptop also has USB IOGEAR additional external video card. This is problematic but when unplugged same above behaviour occurs. I've ruled out monitor interference since same blackout after the UAC prompt appears with external monitors plugged in or when rebooted with no external monitors. Any suggestions on how to address this problem?