When SEP (Symantec Endpoint Protection) is installed, Citrix and other Terminal Servers slow down or become unresponsive. There may be multiple SEP system tray icons and/or the Task Manager Process List indicates multiple instances of SEP processes.
Symptoms
Symptoms include one or more of the following, usually increasing as additional clients log onto a Terminal Server
SmcGui must be disabled to avoid multiple instances of that process and the SEP tray icon by adding the following DWORD registry value on the Terminal Server:
HKLM\SOFTWARE\Symantec\Symantec Endpoint Protection\SMC\LaunchSmcGui = 0
When disabling SmcGui, the following functionality is also disabled:
Note: Duplicate SEP system tray icons in the local system tray of a Terminal Server client may be the result of a Citrix feature called Seamless Desktop Integration, where server resources are made to appear as if they are running on the client. See Symantec Endpoint Protection: Duplicate system tray icons appear on Terminal Server Client for each connection to a Citrix Server
Reference: Citrix and terminal server best practices for Endpoint Protection