Something external not included compliling error

using CUDA 1.1 and VS 2005 on XP.

get this error:

error LNK2019: unresolved external symbol _cudaEncrypt referenced in function “public: virtual int __thiscall GPUAESDef::encrypt(struct CryptCtx &)” (?encrypt@GPUAESDef@@UAEHAAUCryptCtx@@@Z)

any ideas where i need to include something else? function is implemented in same as extern “C” cudaDecrypt() in

I guess a better question is where should this be be included? header, cpp file? any comments appreciated.