laptop disconnects from network

I have a Toshiba TECRA Centrino laptop XP Pro., 512MB, 40GB. Outlook 2003. It has a docking station.

The laptop disconnects from the network at around 3:30 to 4:00pm everyday. And sometimes it will have an error “insufficient system resources exist to complete the requested service”. I’ve scanned using A/V and Anti-spyware and it’s clean. I checked the task manager CPU usage, every 30secs. or so the cpu usage jumps between 92 to 95%. I also checked the System Configuration, Startup tab and made sure nothing unsual is running.