Flickering on startup

Afternoon, folks.

These past few days, I've been experiencing an issue that has me somewhat baffled. When I boot my computer up first thing in the morning, my screen flickers. It's a strobing effect of sorts. I can still see the screen. The picture is fine, aside from the flickering. No colours are out of place or anything of the sort. This problem occurs during POST, all the way through to the windows login screen, and then suddenly stops. I can reboot several times and not reproduce this problem. It only occurs when the computer has been off for a period of time, say, a few hours.

Obviously, it's not a driver error or it wouldn't be occurring during the initial boot up. The video card itself(XFX GTS 250) is about a month and a half old and has never experienced this problem up until four days ago. Now, it's a morning routine waiting for the flickering to stop before I can login.

Suffice it to say, I'm a little dumbfounded here. I've seen many hardware failures, but none like this. Assuming the problem is with the video card at all, do you think it could be a temperature issue? Room temperature in here is fairly mild. The card itself never runs any hotter than 40 degrees Celsius when I'm running typical windows apps. And this problem never occurs while I'm running windows apps or playing games. It's only during the initial 40 seconds or so of the first boot up of the day.

Has anyone had a problem like this before? Any ideas of what could be wrong?

I've swapped the cables. That's not the issue. I'm not sure about the monitor, though. In the past, when I've encountered a failing video card or monitor, the problems are usually intermittent or they happen once and poof! it's dead. If it was the monitor, I would expect the issue to be intermittent. This problem only happens during startup after a long period of the computer being shut off. Both the monitor and the card work beautifully during normal operation.

I just find it very odd how this problem is very specific. As I said, most progressive failures I've encountered started with intermittent problems that occurred under random conditions.

Some extra info: The monitor is a Samsung 226bw(original 'S' version), and it is connected with a DVI cable.