Screen freezing when coming out of "sleep" mode only.

I'm posting this here because it seems to be either a monitor or video card issue. If this is the wrong place, I apologize. Please advise.

When I shut down for the night and reboot in the morning, everything seems to work fine.

When I put the system to "sleep", or it goes to sleep on its own, that's where I run into the issue. Somewhere between 20 seconds and a minute after awakening the system, the screen freezes. Nothing I do can unfreeze it. I have to do a hard shut down and then reboot. After that it's fine.

Yesterday I awakened the system, quickly logged into Netflix and started a movie. When the screen froze, the movie was still playing. That's why I think it's either the monitor or the video card. Obviously the computer is still working just fine behind the frozen screen.

I am experiencing absolutely no other issues with my system. My anti-virus is active and up to date, and running a scan produces a perfectly clean bill of health. Not even a single suspicious item is turned up (which I suppose is suspicious in its own right).

Any ideas?

Vista64 Home Premium Service Pack 2
Intel i7
NVIDIA GeForce GTX 285
Acer H233H Monitor
Kaspersky Internet Security 2014 (running and updated nightly)

Thank you in advance.

Frank