What version are you running? There were some issues in RU5 and ealier that are fixed.
Follow the migration path in the following KB.
http://www.symantec.com/business/support/index?page=content&id=TECH145428&actp=search&viewlocale=en_US&searchid=1294938757629
BSOD with Teefer2 driver on MR5
Fix ID: 1850556
Symptom: BSOD caused by the Teefer2 driver
Solution: Code changes to lock NDIS miniport block and copy information into local variable, preventing the crash.
Occasional Blue Screen of Death on Vista and Windows7
Fix ID: 1868542
Symptom: Computer experiences a BSOD because wininit.exe terminated abnormally on Vista or Windows7.
Solution: Changes made to prevent the Blue Screen from occurring, and to minimize the number of hooks into system threads.
http://www.symantec.com/business/support/index?page=content&id=TECH103087&locale=en_US