Could you try two thinngs first?
1) find the pid of the java process for zdesktop background service and do a 'kill -3 <pid>'. The process stack will be written to <install>/log/zdesktop.out. That will show us if there's any real lockup.
2) do a reload in the gui window by shortcut key 'shift+F5'. see if that was simply a gui freeze.
Thanks!