VMWare Server Error: Invalid character class name

[Buildboy]

Hi,
I have been using this action successfully to start and shutdown the remote VMs ( Windows 2000 all flavors) , however when I attempt to do the same for Windows 2K3 the step runs and the VMs are started or stopped, however the step fails instead of showing completed with the following error

Waiting for guest OS to start...............................
Invalid character class name
1/4/2007 2:14:00 PM: Step 'Start VMware Server' failed
1/4/2007 2:14:00 PM: Build ended.

I would appreciate any help and explanation greatly,
Thanks