[neilbyrne]

I had this problem so bad that I did a clean install, destroying a career in which I already had two CMOH and it was only the end of '42.
I have subsequently tried to stay within the guidelines above altho I don't think it's that necessary.
What I have seen work best is that you have to let the program run until it's happy to stop. What I mean is if something big is happening, like you're taking damage/sinking, and you just want to abort and re-load, don't do it. Let it run out and then re-load. Also don't try to switch screens fast if something complex is happening. It seems to stay more stable under these conditions. No need to reinstall either. When the problem does occur, it appears to clear at the end of that patrol.
I just completed a patrol in which I torpedoed eleven ships and saved the approaches to same multiple times with no problems holding to the above guidelines.