If you have Host Checker enabled I suggest disabling that and testing. As a next step, I suggest updating the Pulse Desktop Client version to the latest.
It may also be related to:
I too am experiencing this same issue on a brand new machine. I can connect succesfully once on a brand new boot, but after I disconnect, I can't reconnect and get met with the error :
Failed to setup virtual adapter. (Error:1205)
Restart your system and try again. If the problem persists, contact your network administrator."
It would seem this issue has been going on for other users for months, has there been an official solution to this other than restarting a PC everytime we want to reconnect?