Did not receive cluster membership. Manual intervention may be necc...

As Hywel mentioned, lltstat -n (or lltstat -nvv for very verbose output) is your first port of call. "lltconfig" is also a good command to make sure llt is loaded. 

gabconfig -x is really a safety override... make sure you are only running this command if you know what you are doing... if you don't know why you shouldn't sometimes run it, DON'T RUN IT! call support.

Do you have any servers that are out for maintanence.