I had this problem happen all during beta and was hoping it would be resolved in the release client, but unfortunately it isn't.
Basically every 5-30 minutes I get kicked back to the login screen with the error "An unknown error has occured" and I have to relog back in.
This also also rolls my character back position wise, although I retain items, XP and quest status. But it gets annoying travelling all the way across a zone and then being put somewhere I was at 10 minutes prior.
I know several others were posting about this during beta as well. Has anyone found a resolution?