[helicase]

That happens to me all the time in 3ds max 7, Sure its anoying, all I do is save a lot, and work with not many polys on the screen, then i use bounding box when i am doing rendering stuff. Also make sure you are not working with nurbs, or modifying the mesh when NURMS is on. That might cause problems. Good luck! Its hard to trouble shoot for other people, perhaps tell us what version of 3ds max you are using, how high the poly count is when your working. If you got 3ds max legit or from torrent. Things like that are very help full.