We have had issues at times with not being able to open a remote psexec session because of the service already existing on workstations and refusing to start.
This powershell command prompts for credentials and stops the service if running and deletes it so you can open a new session.
powershell.exe invoke-command -credential user -computername {smartname} {stop-service -name psexesvc; sc.exe delete psexesvc}
