Scanjet 3800 connected to Pavilion 6105a.de doesn´t scan

Installation of the german software included in setup_full_3800.exe (from
15th May 2007) for windows vista on a pavilion 6105.a works fine
(virusscanner/firewall disabled). After the installation I connected the
Scanjet 3800 via usb to the pavilion 6105.a and the scanner was detected by
the operating system. Everything seems fine, but scanning is not possible
(no error message). After pressing the scan button of the scanner HP
Scanning is launched. But after selecting the scan button in this
applikation nothing happens (no error message, no scan, simply nothing). The
scanner works fine with compaq nx8220 and vista business operation system,
the same software (from 15th May 2007) and installation procedure.

How to get the scanner running with pavilion 6105a.de and vista home
premium?

Thank you,

Dirk Lehmann