Three things:

1) How many files are you sharing? I only share about 40 now - the more shared the slower the program. I shared my whole hard drive once to see what would happen and the program came to a grinding halt.

2) I only keep up about 5 servers now.

3) When all else fails completely shutdown your computer and run Scandisk when it restarts. You might find a few bad sectors on your disk which are causing problems.