A Terminal Services client may be unable to connect to a Terminal Services license server installed on a Windows Server 2003 computer.
This behavior will occur if your backup program uses the VSS (Volume Shadow Copy Service), the Terminal Server Licensing administrative tool contains expired Terminal Server CALs (Client Access Licenses), and the Terminal Services licensing pool is empty.
This problem occurs because the process that recovers the expired CALs from the Terminal Server license server did not restart when the Volume Shadow Copy Service finished the backup process, even though the Terminal Server Licensing service works with VSS.
To workaround this behavior, schedule the following batch to run every day, after the backup:
net stop TermServLicensing
@ping -n 4 127.0.0.1>nul
net start TermServLicensing
NOTE See How Volume Shadow Copy Service Works