Vexing Video Issue

[LIN1B09]

I have a belligerent 5800 Ultra that shows only its own information (GeForceFX 5800 Ultra, 128MB, etc.) immediately after startup, then nothing. The motherboard, an Abit NF8, will not POST after this. All other components in the system are fully functional and stable, because when I substitute a GeForce 3 for the 5800 Ultra, I have a fully functional rig.
The 5800 Ultra in question has been modified from its original design because I can't tolerate the Dustbuster aspect of its cooling apparatus. I removed the soldered-on heatpipes and heatsink, then removed the remaining solder, which left a very sizeable flat plate. Using Arctic Silver Epoxy I affixed a PC Toys/Zalman all-copper flower-style heatsink. The idea was to then cool this ginormous (918g, I believe) heatsink with silent fans, which would move far more air with much less noise than the original FlowFX system.
I realize that in all probability I was overzealous and killed the card, but it still shows some sign of life, and I'm miffed about what next.

The rig in its entirity is as follows:
BFG GeForceFX 5800 Ultra / eVGA GeForce 3 Ti200 (stand-in card)
AMD Sempron 2800+ AIO3BA @ stock
ABIT NF8 nForce 250gb
512MB Crucial Ballistix PC4000 (512MB x1 in DIMM 0 position)
Cooler Master ACLY 450 Watt
Asus Quietdrive 52X CD
Asus Quietdrive 52X CD-RW
Mitsubishi Floppy
Maxtor Diamondmax 10 PATA133 200GB 16MB cache
Turtle Beach Santa Cruz
Chaintech AV-710
Cooler Master Hyper 6
No case; mobo flat on desk

 

[Quinton McLeod]

There's your problem. You modified your video card (and re-sodered). There's no telling what circuits you may have binded together with soder. Good luck on getting your computer fixed, because I can't help you.

 

[LIN1B09]

Actually, I didn't use solder, although I suppose the Arctic Silver Epoxy could have been conductive. But there was always a copper plate between the board and the epoxy, and I made a splatter guard of sorts to prevent stray epoxy from somehow making its way around the plate.

 

[BadThad]

Bah...just pitch that card man. They go for about $50 on the used market anyway, nearly worthless. If you want an even better cheap card, check the ForSale forums here. You can find a 9800Pro for ~ $80 shipped and it would smoke that 5800.