I have checked to make sure there is no snapshots or log files
Where did you look for the snapshots? Snapshot Manager may not always show the snapshots. Please open the datastore browser to see whether there are <vmname>-00000x.vmdk files in the VM's folder. Depending on the ESXi version you are running you can either "Consolidate" snapshots even if they don't show up in the Snapshot Manager, or simply create a new snapshot and then click "Delete All".
Note: Although very unlikely, but in case you are running ESXi 4.0 prior to Update 2, remember that deleting multiple snapshots using "Delete All" may require a certain amount of additional disk space on the datastore to succeed!
André
