Ahhh Yes, Mandrake 9.1 and KDE with supermount. I do not known what makes it do that, so do not worry it is not you, maybe try another destro. I have run Mandrake distos since 6.0 with out any big problems until 9.1. 9.1 did the same thing to my machine, what a mess, dropped back to 9.0 and some of its wacky problems, but at least it stays up better than 9.1 ever did. I guess 9.1 does not like mine or your machine.
All I have to say about Mandrake 9.1 is, " Linux is not ment to work that bad ".