Since some weeks i have a problem when opening files or Directorys. A Requester apears, and the files i try to open are unusable. Does someone else have these Bug to?

This is no bug, but a feature. The structures on your HDD got somehow corrupted. Eg. some buggy program trashed the memory of disk buffers, and this trash got its way to the HDD, or you've a Peg1 w/ IDE DMA bug and it trashed data while writing, or maybe your HDD got a bad sector. SFS pops up this requester to let you know there is a problem. There are good programs which will attempt to repair the filesystem on the disk, but better, remove any useable data from that disk, format it, and copy everything back. That will surely eliminate all problems. (Hopefully.)

Problems like this are pretty rare anyway, i didn't had such problem since ages, not on my Pegasos, and not on my Amiga(s). You just had bad luck...