I had such issues earlier in 4.0 time frame. Only VI client used to be non-responsive and later [Not responding used to displayed] had to kill the same and restart the process.
I had the suspect on antivirus playing a role in it. However, I encountered same issue without antivirus also. I did a complete uninstall of the vi client and remove the temp directories, restart my windows, and installed the client again. It was working like a charm till I had de-commissioned it.