Video at boot until desktop appears but then no video

Hi,

I have a Sapphire Radeon 6950 no more than six months old. Recently I have had some strange fan noises. They are not all the time but from time to time. When I shut down and wait before rebooting the fan noise becomes normal again. I don't know if it is the video card. I did air dust my computer as I normally do from time to time. I have my video card over clocked using Trixx utility. The clock speeds are GPU: 850 Mhz and Memory: 1300 Mhz. I think I am going to undo the overclocking. It is the OC edition card so it came at 820 mhz and 1250 mhz.

So the main problem is now when I boot in the morning I have video until the desktop appears and for maybe a few more seconds after. Then the screen goes black and "no signal" appears. I tried to unplug the HDMI cable with the HD TV off and then plug it back in and turn the TV back on. That does not work. Because it is Win 7 I cannot do a Ctrl+Alt+Del twice and restart since it brings up that "interface" Since I don't know what it is exactly called. So I hold the power button, turn off unsafely and wait to start up again 20 seconds or so.

At that point the video stays on just fine. Today makes the third time this has happened. I hope my card isn't going bad. Should I contact Sapphire and see about the warranty? Or is there a bug with the new AMD driver? Something else?

Thanks