My advice is to reload your last save game and try again, if it still CTD then load the save game prior to the latest. You do use more than a single save game file, don't you?
I typically use at least two save game files for each patrol, MISSION_## and MISSION_##_PATROL - and alternate saves between the two files. I will save the game after, or before a major event like inserting troops, entering a port for photo recon, attacking a task force, upon reaching the 1000 mile radius of my home port, etc~ It may not be the best method, but it prevents me from losing to awful much if something goes horribly wrong like it has with you.
Save game files can hold a LOT of information and the more info, the more likely that something will be screwed. It doesn't happen often, but it does happen. I am never afraid to save a game at any time, day, night, surfaced, submerged, contacts, no contacts- it doesn't matter much for me. But other people insist that you should treat saves like fine china- save on the surface at full stop, calm seas, no contacts, etc~ To each his (or her) own, I suppose.
