Have you made SH4.exe large address aware?
This thread is the method I used.
http://www.subsim.com/radioroom/showthread.php?t=202192
My game used to crash every time I got near a base; I didn't read the reports though. (I don't know if it was the sound module.)
I too run a Steam copy of U-Boats with TMO, RSRDC, OTC, and Traveller's. I recently reinstalled and forgot to make it LAA and was getting crashes as soon as I looked at anything outside the boat. It hasn't crashed again since.