When performing the Undo command the following error message is being displayed:
Unable to create temporary file for undo: C:\....\....\Temp\msundo. Undo currently disabled, changes made to the file will not be able to be undone.
While editing any open file in MicroStation it is not possible to undo any changes made to this file.
Check that there is write access to the temp directory listed in the information message being displayed. This is where MicroStation writes the undo changes. i.e. msundo1, msundo2, etc. If this user logged does not have write access to this file or folder this message will be displayed and they will not be able to Undo any changes made to their files.