A hotfix has been released to fix a crash caused when repeatedly and quickly stop/starting an outgoing queue.
941560FIX: A general protection fault (GP fault) error occurs when you restart an outgoing queue in Microsoft Message Queuing 3.0
This doesn't sound like something many people will encounter - maybe if you have some code that pauses the outgoing queue when the destination is full and unpauses it when there is space, depending on what logic you have programmed in.
The hotfix requires Windows 2003 service pack 2. Windows XP has a different code tree so won't necessarily be affected in the same way.