Access violations are normally caused when jj2 tries to read/write to a part of memory where it is not allowed to do so. Most of the time this is the fault of a bad pointer, which is the result of "bad" jj2 coding and lack of error checking. The only thing I can currently think of, which results in an AV is when you place a trigger/scenery event on a flipped animating tile, but there are definitely more. If that level is the only place where the AV occurs then its probably a matter of level design itself. Otherwise there can be something wrong with your jj2, likely your animation library.