Avid Pro Audio Community - assertion in "..\Mdie_TrackPlayer.cpp", line 469 / access violation/ DAE error -9400

So I'm new to pro-tools and computers which makes this all the more fun. I've been getting the DAE error -9400 when dealing with multi-track drum editing while using the rythmic elastic audio algorithm to do some reasonably dense edits. (And then arranging/crossfading). It's strange though because it seems to only happen when I playback certain regions, but if I trim the front or back, playback works just fine if the timeline starts on a different region (but still has the error once it reaches the problematic region). However, soon afterwards more regions do this until I close the session and reopen it, and everything works fine until the next time (sometimes 2 hours later).

I've also had some "Access violation" and "Access violation" followed by something along the lines of "no/missing/can't find NTTI data" dialogues. These access violations are immediately followed by: assertion in "..\Mdie_TrackPlayer.cpp", line 469. I'm not sure if this has anything to do with the fact that I initially recorded the audio onto a FAT32 formatted USB external drive with PT 7.3cs6 and then brought it home and transfered the files onto my own computer 7.4cs5 (NTFS)? No clue. Any help would be very much appreciated.

Oh and yes I've deleted the databases and preferences, I've got the hotfix and dual core optimizer, I've gone though the display settings, got rid of startup items (gone though the troubleshooting thread).

Thanks guys.
Dave