Tv-out goes dead after five mins. (9000 Pro)

Hi all, hope you can help me with this bizarre prob. I have a Excalibur Radeon 9000 Pro 64 with tv-out. Now before I go on, this is not the "black mediaplayer, but I can see desktop" thingy, really need help on this so here goes.

During boot, image on tv works swell but after a while the tv just goes black. I have to reboot for it to function again. The time frame varies a lot, it can be 5 mins or it can be 2 hours, nothing I do seems to reproduce the problem. Even if I touch nothing, not even logging in this happens. I have tested to reinstall OS as suggested in another forum (use to owe nvidia), tested every known ATI driver, 4in1, numerous keboards (don't ask :-)) but to no avail. I even changed color on the mousemat, it has solved problems before!

My guesses on possible problems:
1, My Radeon is simply broken on delivery. (Great.)
2, Temperature issue. (Not likely, computer room is REALLY cold/open case.)
3, Software/hardware conflict. (But where?)
4, Poor power supply. (Suggested on another issue abt ATI in here, currantly 300w.)
5, To long svideo cable. (15 meters, but it woked like charm on a Nvidia TNT.)
6, Faulty Tv. (See #5.)
7, Bad power in outlets, ie. powerspike. (Gasping here.)

My specs is: KT7raid rev1.0 with latest bios, Athlon 1GHz T-Bird, Excalibur Radeon 9000 Pro 64Mb with latest/all drivers (tho did not test 2600), Win XP Pro, Via 4in1, 15 meter hiquality svideo cable, fairly new working Tv.

Personally I would go for #1 or #4. Everything that I have, has worked with my old TNT card, so that kinda rules a lot out. Hope any of you have/has this prob and can help me.

TNX VresiBerba //

Thanks for your input, Frisbee. However I don't think it's the cable since it woked just fine with my old graphics card, my Nvidia TNT. To test another cable (shorter) I have to rearrange my whole flat 8-{, or buy a new/other one. Infact I think I just proved that point below.

Tho I'm quite stumped at this problem, I got an spendid idea: enter CMOS setup, watch some Tv and wait. Whaa! Tv-out image still there after about two hours, huh? This kinda rules out #1 as well as #2, #4, #5,#6 and #7 (or just a coincendent). It would seem that my WinXP Pro SP1 is somewhat poorly configured, or I screwed up my CMOS settings. The only downside other than it still dosen't work in XP, is to have watched some two hours of my CMOS setup on my Tv, boring to say the least!

I should be able to fix this with a little help from you guys, is it soley a XP prob or a complicated relationship with bad CMOS settings, ABIT KT7raid, XP/drivers or/and the fact that the Radeon share IRQ with 5 other things: Raid controller ((HPT370) not used, my new Baracuda IV refuses to boot on it), two USB's (neither used), NIC (used a LOT) and the ACPI? Comon guys, ANY input on this would be very appreciated.

VresiBerba //