error after cuCtxSynchronize

I’m writing a CUDA program to do long lists intersection…unfortunately I couldn’t install Nexus on my laptop and so I can’t debug the kernel…I revised my kernel code and seems not to have any problems but what I get when I do cuCtxSynchronize() after the kernel launch is CUDA_ERROR_UNKNOWN
P.S I’m using CUDA dirver API
so what are the causes of this error??
Thanx in advance