First thing is to log in. Just try the sqlcmd without any -q and see if you can get a connection to the server. If not, is it saying that the transaction was rolled back in the trigger, or is it just saying that login failed.
Once you're in, it's easy to get the trigger name from the sys.server_triggers view
Also, the syntax is
ON ALL SERVER, not ON ALL SERVERS
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability