I have a Dell Latitude D520. First with Windows XP and now with Windows 7, it completely freezes/locks up if I dock it while it's awake. If I hibernate/sleep, dock, then wake/resume, everything's fine.
I installed the Dell Notebook System Software for Vista (No Win7 version available) and updated the bios to the latest version but the problem persists.
As long as I remember to put this thing in standby before I dock it, it's extremely reliable--it survives my daily commute and heavy use and typically only reboots a few times a month.
Any other ideas for things I can try?