If you have older clients reporting into a newer SEPM, it's possible that changes in the database schema are causing this reporting weirdness. I definitely recommend getting all clients up to at least where your SEPM is, 11.0.6005 (RU6a), preferably get everyone up to 11.0.6100 (RU6 MP1). [Oh, I see you have updated.]
Perhaps use the dbvalidator to ensure the database doesn't have broken links. What type of server is the SEPM on, and do you access it through RDP (and if so, is it a console session)?
"How to use the Validation Tool for the Symantec Endpoint Protection Manager Database."
http://www.symantec.com/docs/TECH104892
Some admins disable telnet, so the fact that you can't telnet may be a red herring. Do a netstat -anbo | more (in a command window on the SEPM) and look to see if dbsrv9.exe is listening on this TCP port (provided the DB is the embedded DB).
sandra