there's a known issue with PGP tray having high utilization, this is caused by the netshare dll. Unregistering the netshare dll has helped, i've only seen this issue on a windows 2008 server that was used for a terminal server. the first user is fine, but then additional user's login and then PGP tray users 50-60% CPU.
https://www-secure.symantec.com/connect/forums/issue-pgp-desktop-101-using-25-50-processor-time