I have been using the webchat and have had the same issue for a long time.
When the server restarts the fastpath service fails (when i click to open the workgroup i get a list of errors) and i have to uninstall the plugin (not the webchat part just the service) and reinstall it for the service to start working. This only takes a few mins but all logged in users dont not appear online until they close spark and re-login then they will appear in the workgroup as being active.
This is becomming a bit of a PITA and i do not have any idea how to fix it or what information one of you guys need to help identify it.
i running windows server 2008 rc2
nothing really special about the setup to be honest
hope you can help