You should get your IT department involved on this. Sounds like you have a compatibility issue with a SEP update and your wireless drivers. Hopefully you are running the latest version of SEP. If this is SEP 11, RU7 MP1 is the latest. If this is SEP 12.1, then RU1 is the latest version.
Note that there is a reported issue that is fixed in SEP 12.1 RU1.
Network connectivity is lost after installing SEP 12.1 on a client running Microsoft Windows Live OneCare 2.x
Fix ID: 2479660
Symptom: After installation of SEP 12.1 on a computer already running OneCare 2.x, network connectivity is lost. The user cannot connect to the internet or shared drives.
Solution: The sysplant.sys driver (Application and Device Control) was modified to allow OneCare 2.x to load correctly.http://www.symantec.com/business/suppor ... TECH174565
In the future, the best forum to get support for Symantec Endpoint Protection is the Connect Community.https://www-secure.symantec.com/connect ... -antivirus