I have been having a similiar experience. Either I get the [Admin] message or get removed from the map after 10-15 seconds. Sometimes i get lucky and manage to complete the mission. It all seems extremely random.
As it turns out this is one of the older bugs of STO and STILL has yet to receive any sort of decent fix. Some people have gone months without being able to get in and some get in with the next regular maintenance. Trouble tickets won't help at this point because it's just so old of a bug both PWI and Crycptic could really care less. Sorry. :/
could you drop by the red alert channel if you aren't a lot of us are experiencing multiple game issues (exchange mail, dili exchange so forth) or just a post your aware so your not getting thousands of tickets for the same thing.