Just a few thoughts on this from what I have seen using Windchill 8 and versions WF2, WF3, and WF4. When I tested going to WF3 from our current build of WF2 I found that my Workspaces got corrupted and could not be accessed if I went back to WF2. Same with WF4. I would have to guess that if you did not remove your Windchill or PDM cache prior to going to WF4 that there is some sort of corruption going on. Could be wrong, I know that when I tested WF4 recently that a warning message came up saying something like it was going to update the cache and would not be usable in older revisions of Pro/E. What I do to go back and forth between revisions of Pro/E is I go to the "source" of where the cache resides. I have a cache folder named for each version and just rename them to what I need at that time. (example; C:\Documents and Settings\username\Application Data\PTC\ProENGINEER\Wildfire) This is the folder location and Wildfire is the folder that I rename. Under the ProENGINEER folder I have a 3Wildfire, a 4Wildfire and the "active: Wildfire folder. So say I want to switch from WF2 to WF4 I first shut down Pro/E and then I rename my Wildfire folder to 2Wildfire and then I rename my Wildfire4 folder back to Wildfire I can then launch Pro/E WF4 and all my workspace appear and function properly. So in your case I would try renaming your current cache (Wildfire) folder and then relaunch Pro/E. You will have to re-set your Server Registry which will create a new Wildfire folder for you and see what happens. Just something to try if you haven't got any help yet. Craig