Symantec AntiVirus is the only cause of my computer crashing

Symantec AntiVirus is the only cause of my computer crashing.

When my computer crashes and I am forced to hold down the power button for 6 seconds in order to force a shutdown, upon restart I am always presented with the Symantec "SCAN NOW" dialog box.

 

What seems to trigger this crash is when I switch "Apple Menue/Locations" from one setting to another (ie. ethernet to wifi)

 

SYSTEM DETAILS: 

Mac OS 10.5.7 (same problem with 10.5.6)

MacBook Pro  2.5 Ghz Intel Core 2 Duo

 

SCREEN SNAP SHOTS:

Symantec AntiVirus 10.2 (17)

http://tinyurl.com/p2c2ye

 

Scan Now Dialog Box

http://tinyurl.com/qw5d2a