I had the exact same problem after renaming the (NT4)machine and inserting it into a domain. Also the application manager would hang on loading.
Removing it from the domain caused the Application Manager to load, but display the applications with a question mark on them and told me they were read only. Administrator program still hung on startup. I did notice in the system registry the Application Manager settings for the apps, listed under keys named as the machine name. Didnt try renaming these, however I suspect this may have resolved the application issue.
Renaming the machine to it's original name resulted in the Application Manager working correctly, however the Administration program still hangs on startup with ~85% CPU utilisation after a few seconds.