Failed to log in

[pschmi]

We try to suspend a Domain in Plesk. After a few seconds plesk answer with the following error.

ERROR: PleskUserException
Unable to activate/deactivate domain: Execute listmng domain "creative-foto.ch" off failed: Can't open domain.
Domain: creative-foto.ch [creative-foto.ch].
Reason:
Failed to log in.

We use Plesk version 9.5.4 for Windows. We changed the windows password. Is this the reason why? Where can we change the password for Plesk?

Thanks very much for your help an best regards from Switzerland.