Could there be a small leak somewhere? Most games pushing 2.5-3 hours tend to end in this crash for some and eventually most players. Before (14) I got this error only sometimes in 15-20 hour games. I'm going to post replays in the bug report section every time this happens, maybe Zwieb will pick out a pattern/common denominator.
About you losing items/XP, the onus is on you to save regularly in war3 RPGs.