If you are receiving the error message: Unable to get local AppData folder then please read below.
Cause
The most common cause of this issue is that Torchlight II has been installed on a machine which is intermittently connected to a domain with enforced folder redirection (e.g., a laptop or a machine on a corporate VPN). When the game was installed, files were added to Documents\My Games, but because of the redirection those files are located on a server which may now be inaccessible.
Resolution
Reinstalling the game may resolve this issue in the short term, but folder redirection will still likely cause issues going forward.