Workstation Scan Failed "No response received from workstation."

Hi everyone,

we have installed ServiceDesk Plus 7.6.0 Build 7605 and the Workstation Scan does not work as dependable as expected.

I encountered the following Error Message on serveral Machine
FAILURE :No response received from workstation. Probably the workstation might be switched off or does not exist.

I tried the following on a single Workstation (WinXP):
- Open Port 7 TCP (for ping)
- disable Windows Firewall
- Run the Script from this Thread: http://forums.manageengine.com/#topic/49000003531092 (although I don't know which Ports I should use. I used the Ports TCP 5000 to 5002)

But nothing seems to work.

The Workstation is pingable from the ServiceDesk Server.

Do you have any suggestions what I should try next?

Thank you for your help,
Nils