Availvidmem & Totalvidmem Bug

I am getting
totalvidmem = -1648644096
availvidmem = -1672968604

(but UsedvidMem seems to be reporting a correct figure)

I am running:
Blitz3D 1.99

Computer:
MB: Gigabyte P35-DQ6
CPU: QuadCore Q6600
Memory: 4 GB
GFX card: GeForce 8800GTX (768 mb) and official drivers 7.15.0011.6369 (according to DX Diag which is also reporting 2523MB of video memory)
OS: Windows Vista Ultimate 64bit with DX10

Anyone else with this problem or can I provide any more details to help out to isolate where things go wrong?

I assume this is a driver problem.

Note that Blitz3D TotalVidMem reports the same wrong value as DX Diag, but interprets it as a signed 32-bit integer.

( Blitz3D TotalVidMem ) = ( DX Diag value ) - 2^32

Well spotted. You think the best solution is to just detect when vidmem-commands are showing negative results and assume it's > 512MB cards?

I am currently using these commands to detect wether videosettings should be reduced and it now thinks it's ran out of memory.

This is a bit over my head.

Can you come up with a (Vidmem conversion) formula that will work with all graphics cards?