I mostly tell people off for bumping this sort of thread
My excuse is that after all the years of posting of tips on the forum, I have finally managed to post an answer to a problem with XenCenter that I have not seen elsewhere on the net
I'm also quite relieved! we have been running XenServer since October and it has been virtually trouble free.
Today the Ford forum client I have been working on locked itself in a halted state when I tried to reboot it, and none of the recommended non brutal solutions resolved the issue If that sort of thing happened often it would be very bad news indeed.
But happily there is a simple solution the lock can be caused simply by the XenCenter connection to the server, disconnect and reconnect and things start working again