- Do you have maybe Ccleaner software running on this machine? - I remember there were some problems reported with this software - that was starting with computer start and trying to block or remove some of the SEP files.
- Any chance you could install SEP 12.1 on this machine and check if it reproduces the same behaviour?
- Another possibility - corrupted installation package - have you been using the same installation package (from SEPM) for the SEP installation on this machine? If yes try to export a new package from SEPM and do a new install using it.
- do you find any errors in the Eventviewer when system starts that may be related? (like example:
http://www.symantec.com/business/support/index?page=content&id=TECH131595)