[2015-06-24 10:45:34] Starting on stratum+tcp://pool.drop.software:3000
[2015-06-24 10:45:34] NVAPI GPU monitoring enabled.
[2015-06-24 10:45:34] 2 miner threads started, using 'drop' algorithm.
[2015-06-24 10:45:35] Stratum difficulty set to 0.001
Cuda error in func 'quark_blake512_cpu_init' at line 231 : invalid device symbol
.
C:\Users\Programmist\Desktop\drope>pause
I think that means your card is not supported due to a low compute version. 3.5 is minimum I think.
Check https://developer.nvidia.com/cuda-gpus to find your compute version
GTH 660 is not supported? : D