Problem with Acronis DriveCleanser

My Product: Acronis True Image Home 11 (Build 8.105)

OS: Windows XP, SP3

Hi,
I encounter difficulties when I attempt to format an external HDD that is connected via USB port.

My step by step is as follows:

Harddisk Tools - Acronis DriveCleanser

Select the external HDD (NTFS formated)
Choose Keep Partion on the Pre-Action Tab
Type of Delete-Method: VSITR (Deutscher Standard)
Click Finish and confirm message with Ok

Now I get an Win32 exception WiperTool.exx [644]

Any help on how to troubleshoot is greatly appreciated.

Thanks
Bodo