Monitor Problems

I just conducted a rebuild of my main system which basically involved whacking a Fenrir on the CPU and a 5850 replacing my 8800GT, but I took the opportunity to rewire (attempting to make it neater), de-dust etc. Apart from those changes system is as below in sig or in "My System"

Anyway a problem has reoccured that this system used to have, whereby it intermitantly refuses to output video. The monitor just sits on "No Signal". No error codes (and usually I hear the windows chimes as it boots in) Its not to do with the graphics card, I'm 100% certain, this same problem has happened before with the 8800 GT and the 2900XT that preceded it.

The monitor (in this case TV) is also fine, have tested with multiple monitors, using DVI, DVI-VGA HDMI cables, and when the problem occured before I was using a different monitor

At the moment how it is manifesting itself is that when I reboot the PC, the signal goes unless I cut the power and then the PC will turn on fine video and all.

I know it sounds like a video card problem but a this problem (albeit not from restarts but from cold starts) was actually the reason I swapped the 2900XT for the 8800GT, which made no difference, although the problem just seemed to magically resolve itself one day.

I havent described it very well, I've got a feeling its a motherboard problem, occasionally after ive powered off I get "CMOS checksum bad", although I think that might be connected to my solution to the problem, rather than the problem itself.

Any suggestions welcome! It just strikes me as very odd it could be a hardware problem when I can still hear the chimes of booting. Its almost like the motherboard isnt using the graphics card or something, but that would usually give a beepcode and POST fail wouldnt it, seeing as how my motherboard is without integrated graphics.

Dodgy video cable or socket ?

Doing some (more) googling (hard to find relevant search fields) it appears some people are having this problem with the P5K if the graphics card is pushed too firmly into the PCI-E slot, so I'll try loosening it up. Strange that its fine if the power is cut though.....