Error message when updating collections

Hi there,

I am having this issue now since a few days. When I try to update some collections (in Altiris Deployment console 6.5), I get the following error message:
"Changes to the collection could not be saved because an unexpected error occurred"

It happens on some collections, not on all of them.

I now noticed that even the "auto-update" of the membership (via filters) doesn't work, which means I cannot install machines correctly anymore.

I really need some help urgently on this. Has anyone seen this or have an idea where to look / what to change, to solve it?

Thank you for your help,
Luke