Exec error

I have recommended gpg4win to several friends, but one of them experiences that right-click on a file encrypted with gpg4win 1.1.3 in GPGee/verify-Decrypt only give the return: “exec error”.

I am not able to give any debug-info additionally.
It is an Windows Vista maschine.

PLease give a brief list of possible solutions even if this info is insuffiencient to you.

I have never had any problems any time with gpg4win on any window machine or gpg on any linux machine.