I ran into the same exact problem with AIP 2009 and this solution worked perfectly. I couldn't do a simple stress analysis update, or preview my mesh. After reregistering the modules, it works like new.
the only problem for me was getting the cmd path correct...for the IT deprived such as myself, i couldn't restart back at the C:, so i found out by typing 'cd ..', it takes you back a folder level. Once back at the C:, you can type in the path, or to be more careful, you can type in a portion of the folder name and hit the tab key, and it will auto-correct to the closest match, i.e., \pro (tab) took me to the program files folder, then \auto (tab) -->autodesk, etc.