The problem you are experiencing is probably due to the program being unable to open the same port that the first instance of the program has already opened. Switching profiles will not free up the ports already opened by programs/services on the first profile.
I can't think of a good, compelling reason to have this feature enabled in an AD environment. You can disable Fast User Switching via GPO under Computer Configuration, Administrative Templates, System, Logon. Enable
the Hide entry points for Fast User Switching
setting.