I was finally able to solve the iisreset problem :
The following error was generated when "$error.Clear();
Start-SetupProcess -Name "iisreset" -Args "/noforce /timeout:120"
Analyzing the system log i found the following entry:
Log Name: System
Source: Service Control Manager
Date: 26.08.2010 18:27:36
Event ID: 7003
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Computer: XYZ
Description:
The Net.Msmq Listener Adapter service depends the following service: msmq. This service might not be installed.
After installing the Microsoft Message Queuing Server I was able to successfully install Exchange 2010 SP1 - I am glad this happened in my test environment first...
Cheers
Christian