Hmm, well after a night's sleep, I booted the comp up again this morning. It worked fine until when it's loading the startup apps in the system tray. There, while loading certain components, the screen would just black out (but the LED on the monitor would still be green). A conventional shut-down via keyboard didn't work neither. After I reset the machine, I loaded up a song as soon as it got to my desktop. When the screen froze up again, the song froze too - so it wasn't just a screen problem.

I had a hunch that it froze when Nvidia control panel modules were loaded, so I uninstalled and reinstalled the card....several reboots after that have yielded no problems, so I guess it should be fine if I can do a cold start tomorrow.