only deactivated it on the 1712.
all other drives still work fine in dma mode.
its more important to me that the drive is accessible after a few hours without a reboot.
so i think i have to accept this strange behavior since i tried everything to get this drive working.
this has to be a software problem. the drive works fine the first time after a reboot. got the same problem with win2k.
help is still welcome
but finally i got this thing running.