Multiple client computers have the same Symantec Management Agent GUID, which should be a Globally Unique ID. This makes it impossible to properly manage or account for these endpoints.
Computers are deployed using an image which contains a Symantec Management Agent GUID already in use and known to the Symantec Management Platform database.
Note: Currently this workaround is only available for client computers on the Windows platform:
You can also download and import the attached 'Computers with a Shared GUID (report).xml' and 'Computers with a Shared GUID Detail (report).xml' files into the Reports area of the console. These reports show host names currently using a shared GUID, and the recent host names that have shared these GUIDs.
For an Altiris 7.1 best practice to address this issue see:
Shared GUID cleanup script