Hi Tina, could you confirm what your hardware config is, the list you have above does not make sense? Normally you would have a GT120 or Q4000 for UI and a GTX680 for image processing, not all three.
Also, re the XML and trim workflow. The XML should reflect the edit and the clips used in the edit. If you modify the clips after the XML is made, i.e. trim them, then the XML is not valid any more.
Have another try with trim on 9.0.3. It may well be more stable than last time you tried it.
Peter