Hi!
The problem is solved now. After discusions with the manufacturer of the encryption software I just dismonted the disk and remounted it again. But I could not dismount it the normal way, I had to do a "Brutal dismount". This brutal dismount is available in the menu for the encryption software, but is not recommended. I did not even have to reboot the computer.
I set up a new disk and tried the behavior on that one first, repeating all the original steps. Obviously was the data on the disk not corrupted. It was just a mismatch between the cash data in XP and MFT on the disk.
The reason for not rebooting the computer in the first case was that I was afraid to lose contact with the disk and then donĀ“t have the chance to apply a recovery program.
I thank you all for your interrest anyway.
Best regards
Proman