Blitz changes var types in userlibs!?

Well, everything seems to work when I simply don't use STR$(). But then I discovered that SEEK command is broken when used with some higher file offsets. If I 'seek' a position and then check back with SEEK() function I get a different position (one less or three bytes ahead). This makes more complex file i/o impossible. :-(

This really drives me crazy...

PB's support wrote to me that this must be a bug in Blitz, so they won't give me any help solving this. :-((

Mark, what's going on here??