NAVAPSVC.EXE causes CPU usage to 33%

I have recently installed Norton Sytemworks 2004 on a friends computer and have noticed that as long as NAVAPSVC.EXE is running that CPU usage is at anywhere from 22%-33%. It never comes down. If i disable the autoprotect from Norton AntiVirus(which is what this program is) then my CPU usage goes down to around 2-4% which is where it should be.
The computer is confugired as follows:
AMD Sempron 2600+
512 MB RAM
ASUS A7v8x-x MOBO
WIN XP PRO SP2
Norton Syswork 2004

I have three other similar computers running this same program and with AutoProtect on thier CPU usage is only at 4%.

Does anyone know why this one computer would use so much of the CPU to run Autoprotect? A full system scan has been completed, and I have made sure that the NAVAPSVC.EXE that is running is from the C:\programfiles\Norton Systemworks\Antivirus folder ,to make sure it is not a trojan or a virus.

 

i have the same problem....can't find any answer on the net...unhappy of this i am