Ah, so if you're using the full scratchpad space right now do you have an idea why I can't use any launch configurations that go over 2.8GB? The program says there isn't enough memory, but according to the calculation there should be. I'm wondering if there is an integer overflow comparison somewhere?
Windows Driver Model, or WDDM doesn't allow for really huge single memory allocations. For this to work you need to run the card either on Windows XP, Linux or Windows with the TCC Driver (which is officially only for Tesla cards). Vista, 7 and 8 use WDDM.
ALSO: On 32 Bit systems or using 32 bit binaries (like cudaminer.exe) one can only address 4 GB of memory on the card at most.
Christian