Possible copy-protect issue

The game tried to connect to the internet several times starting up, but since I was only going to play single player, I didn't let it. About halfway through my patrol, I made an attack run on a convoy. I dashed out in front, dropped to periscope depth, and let them come over the top of me. I got three kills with my first spread, and then I lined up a stern shot with the aft tubes at a slow moving destroyer. I let my shot go, then started looking for my next target. A minute later I looked back, and he hadn't been hurt, the torp hadn't impacted, and I couldnt tell where it went, so I let out another torp and glanced around to see what happened to the first one, just in time to see it complete its loop and slam into my side, killing me.
This is the second time this has happened, and I'm just wondering if it's some copy protection issue, as the torps were set for shallow depth and shouldn't have passed close enough to hit me even if they somehow got told to loop around.