I have confirmed a fatal error in AutoCAD 2010 when attempting to save workspaces in the following conditions:
- You are using an enterprise CUIx file.
- The enterprise CUIx is located in a read-only network folder.
There is no fix with the latest AutoCAD update as of Dec 2009.
However, a temporary kludge is to make the network folder read-write for the users and the CUIx files read-only. (Thanks to Bud at Autodesk for this.)
This is obviously not a great solution but at least it stops AutoCAD from dying an ugly death. Obviously you will want to keep an original copy of the CUIx file(s) in a separate location in case you need to restore the enterprise CUIx file(s).