What version of SEP 11 are you running? A fix was included in RU6 MP3.
Symantec Endpoint Protection client location awareness changes location incorrectly
Fix ID: 2189866
Symptom: A Symantec Endpoint Protection client with location awareness enabled changes locations incorrectly.
Solution: If the TTL (time-to-live) on DNS responses is very short, Symantec Endpoint Protection may incorrectly detect a new location change. Symantec Endpoint Protection was modified to handle very short TTL on DNS responses.
This was fixed in RU6 MP2-
DHCP suffix matching now looks at the active interface and will switch locations
Fix ID: 2077809
Symptom: You have configured your location-based criteria to use a DHCP connection DNS suffix. The client network changes so the rule does not match, yet the client does not switch locations.
Solution: After the computer shuts down and switches to another network interface, the offline interface's DHCP DNS suffix was still being used to choose the location. The client was modified to use the online interface suffix only.
http://www.symantec.com/business/support/index?page=content&id=TECH103087&locale=en_US