I updated my GPU drivers since the 296.10 version is over a year old, but the Mercury playback hack wouldnt work anymore. I was going bonkers all day today trying to troubleshoot the issue. I uninstaleld and reinstalled a bunch of times. GPUsniffer would give the notice that it "did not find any devices that support GPU computation". I went back to the old drivers and sure enough, GPUsniffer would detect it.
I wanted to make this post for people googling issues with the hack involving the cuda_supported_cards.txt file involving CUDA enabled GeForce cards that aren't officially approved by Adobe, and also so the engineers at Adobe can maybe look into their end to see if its the GPUsniffer.exe that is the problem with not being able to detect the drivers, or maybe it's Nvidia's problem on their end that the drivers can't be detected. At least you guys can talk to one another to straighten things out.