Icon for Norton Internet Security 2009 appears on desktop but product will not launch

Hi.  I’ve had a problem for the past couple of weeks with my AV product.  One day, not long ago, the Norton icon was missing from my tray.  I used the removal tool and tried uninstalling and installing many times.  No luck.  I let someone from Symantec take control of my computer temporarily to try and fix the problem.  No luck.  About a week ago, idle time scan said that it detected and fully removed a trojan, specifically, infostealer.bancos. I’ve run a full system scan in normal and safe mode dozens of times.  Clean every time.  No other full system scans have ever revealed any threats.  I’ve tried starting in selective mode, then installing and then starting in normal mode.  No luck.  Tried using the Norton recovery cd.  No luck.  I have no other antivirus products installed and have Windows firewall disabled.  My system is Windows XP, service pack 3, 468mb RAM and still plenty of free space on C and D drives.  Any suggestions?  I’d really appreciate it.