thanks
To give more details: The HDs are USB1.1/2.0 drives connected via USB1.1. After starting copying to the drive, the data rate first increases, then the PC hangs (tested with different drives and PCs). Only a reboot is possible to restart. With an older Knoppix it works fine (kernel "2.4.18"), and with SuSE8.2 it works fine too (kernel 2.4.20), so I don`t think it`s a matter of kernel-version ?!