I just completed The Lost City of the Tol’Vir in Uldum and now I cannot leave the Instance. Whenever I try and leave through the Purple Portal, Hearth, Dreamwalk, or even use the toy Nature’s Beacon, it doesn’t work and I get the message: “Transfer Aborted: instance not found”
EDIT: I just tried again and managed to get out of the instance, so I guess if this happens to you, just wait and try again later.