Problem:  
A PC running Symantec 10.x obtained virus definitions from October 02, 2007 and
has quit working properly.  The definitions do not update beyond this point and
RealTime protection may fail.  An error message may mention a failure with
RTVSCAN.

Solution: 
While logged in from an account that has administrative privileges on the local
workstation, download and run Rx4Defs2.21.exe.  You can obtain the file from:
http://www.ncsu.edu/antivirus/files/Rx4Defs2.21.exe

The application takes a while to run.  After it completes, your system will
have virus definitions from 07/17/2007. Run LiveUpdate to obtain virus
definitions from with in the past 7 days.

If the Symantec local console still indicates the definitions are of 10/2/2007,
reboot the PC and re-run Rx4Defs2.21.exe.