These errors can be caused by problems with processor scheduling in dual core processors. The solution is to assign Pro Tools to run on a specific processor core.

To do this:
1. Launch Pro Tools, but do not create or open a session.
2. Right click on the Task Bar and select 'Task Manager'.
3. Click on the Processes tab, then right-click on ProToolsLE.exe and select 'Set Affinity' from the drop down menu.
4. Uncheck the box for CPU 0.
5. Click OK and close the Task Manager.

You will have to do this each time you launch Pro Tools unless you use and application like THG Task Assignment Tool.

More info on the THG Task Assignment Tool can be found here: www6.tomshardware.com

(from digidesign.com)