For those using Windows XP
In some cases, if you are running Windows XP, just restarting the service will fix the problem.
To restart the service
Click Start, and then right-click My Computer.
Click "Manage."
Double-click "Services and Applications."
Click "Services."
Double-click the "Terminal Services" entry to open Properties.
On the General tab select "Automatic" from the drop-down menu next to "Startup type."
Click Apply, and then click OK.
Right-click the "Terminal Services" entry, and then click Start.
Close the Computer Management utility.
Restart the computer, and log in as administrator.
Reinstall Norton AntiVirus. | 
