I have the same hardware, also on debian sid, and this should really work.
Do you start the kernel with any obscure parameters? Something is a bit weird with your setup. I get
Model: Quadro FX 880M
Video BIOS: 70.16.5f.00.0a
Card Type: PCI-E
DMA Size: 40 bits
DMA Mask: 0xffffffffff
Bus Location: 0000:01.00.0
while your BIOS version isn't recongised properly and we have different DMA sizes?
If could help if you use MSI interrupt handling for the GPU; add
options nvidia NVreg_EnableMSI=1 in /etc/modprobe.d/options.conf
This is supposed to be better anyway.