Have you selected Conservative, Moderate or Aggressive for your storage for VDI VMs ? Here is the link for some more information - VMware View 5.0 Documentation Center
If you have selected conversative, by default it will create 4 times the size of datastore and after that it will not create any VMs on that datastore even if there is space. It will alert you that you are running low on disk space.
Hope this helps !!!