I'm working away on getting our CUI migrated from 2009 to 2010, and running into a brick wall.
The setup we're using is to have an Enterprise CUI (a copy of ACAD.cuix) on the network, which loads in the "firmname-tools.CUIx" file as a partial CUI. The users will then have their Custom.CUIX file locally for them to play with till their heart's content. But we're not that far yet -- I'm still working on getting the enterprise CUIx to properly load the firmnametools.CUIx.
The problem seems to be the ribbon. I can transfer the tab and panels from the legacy file to the new-from-scratch CUIx. I can go into Customize Workspace and have the tab appear there. I then save the CUIx and Apply/Ok. But the new tab doesn't show up! What's more, any changes I make to the panel in the Customize User Interface dialog aren't retained after loading it back up. I have full read/write access to the files in question (as administrator), but nothing is retained after a save.