Here I am with another XenServer issue that was easy to solve but quite difficult to troubleshoot. I have applied a few XenServer updates (I am running XenServer 6.5 FP1), but I started having issues after installing XS65ESP1022 and XS65ESP1023.
Specifically, after rebooting the host following the installation of these two updates, I noticed that my host would not come out of maintenance mode anymore. If I tried to do so from XenCenter I would get an error message that said Server still booting. This of course was not true, since I could access the console on the host.
After a lot of trial and error I found a solution, but it turns out there were at least a couple of problems that I needed to solve before being up and running again.