M6400 docking station makes cpu overload

I have been recently having a problem with my m6400 (8GB ram vista 64) when its docked. after booting its fine for a while, then the cpu starts to overload. the task manager indicates various programs are clogging up the cpu, even the taskmgr.exe can take up to 40% cpu sometimes. normally There's no problem running lots of applications at once. I usually have after effects, firefox, windows media player, photoshop etc running at once with no problem when docked. Now it always seems to heat up when docked, but as soon as I undock, the cpu usage drops dramatically and all is fine again, so its not my applications which are the problem.

The dock normally has alot of stuff plugged in, 4 or 5 usb drives, an extra monitor, printer etc, but had no problems until now, and i've been using it for 5 months or more. i've tried taking out everything from the dock to see if that makes a difference and a bare dock does seem to help, no cpu clogging, so it must be something i am attaching, haven't narrowed it down yet, though, will post back here when i've found the culprit.....

Has anyone else experienced this? Could the dock be faulty? Annoying as I really liked the docks performance until now.....

thanks......