Hmm.. The ids were only separated by a commar and not a space.
It appears that the session has to be active before it can be switched. I successfully switched from my account to "Test Account", when trying to switch back I got the error occured while logging out again. I tested this again, this time clicking on a forum and returning to the forum home with Test Account, and switching back worked fine.
It appears that a bit more work is required with the queries or something, hopefully this issue is fixed with 1.1..