I have the same problem. Searching the OTN I found this thread : cluster is falling apart because of long GCs, what is the proper parameter?
I've configured the packet delivery timeout and timeout for service guardian and going to put them on the server. (Not quite sure whether not specifying the timeouts is the problem.)
But there are still some parts unclear to me:
This is happening to me just once a week and exactly after weekends in the early working hours. (Does is really have to do with the idle time of the server in the weekend? Why just once a week and exactly the first working day? If the GC is really running slowly why it is happening at this time?)
And the last question: Is service guardian monitors only threads belonging to Coherence or it also monitors other threads for possible deadlocks?