From the logs your submitted:
The following error:
‘2014-10-16 10:55:21 485.536 12919 NXSERVER ERROR! X resources are not enough to start another session.’
can occur when the server is not able to find a free display in the range defined by the server configuration.
Default values are:
You can try to increase value set for the DisplayLimit key to see if it helps.
The problem can be due to leftovers from previous sessions. The cleaning procedure to free system resources when a session
failed was not working properly in version 4.2.27. This problem is not present in the 4.3 versions.
We suggest to upgrade your installation to the latest 4.3.24 version.