Is anyone familiar with issue as described below?

After Pack and Go opening the "new" drawing ruins the model. If we open the model before opening the drawing everything stays intact. Can it be caused by frequently using Pack and Go?

Is it reliable to Pack and Go a model multiple times or can it make a model less reliable

ICT is managing the updates of our O.S. (vista) and Ido not know if it is caused by an O.S. update.

Regards,

Gert