Ivanildo, can you confirm that the BOTH files exist:
WindowsServer2008r2-000004.vmdk
WindowsServer2008r2-000004-delta.vmdk
The following lines shows the error related to virtual disks:
2015-08-05T15:44:21.575Z| Worker#0| I120: Unable to find file WindowsServer2008r2-000004.vmdk
2015-08-05T15:44:21.576Z| Worker#0| I120: Unable to find file WindowsServer2008r2-000004.vmdk
2015-08-05T15:44:21.576Z| Worker#0| I120: DISK: OPEN scsi0:0 'WindowsServer2008r2-000004.vmdk' persistent R[]
2015-08-05T15:44:21.576Z| Worker#0| I120: Unable to find file WindowsServer2008r2-000004.vmdk
2015-08-05T15:44:21.577Z| Worker#0| I120: OBJLIB-FILEBE : FileBEOpen: can't open 'WindowsServer2008r2-000004.vmdk' : Could not find the file (393218).
2015-08-05T15:44:21.577Z| Worker#0| I120: DISKLIB-DSCPTR: DescriptorOpenInt: failed to open 'WindowsServer2008r2-000004.vmdk': Could not find the file (60002)
2015-08-05T15:44:21.577Z| Worker#0| I120: DISKLIB-LINK : "WindowsServer2008r2-000004.vmdk" : failed to open (The system cannot find the file specified).
2015-08-05T15:44:21.577Z| Worker#0| I120: DISKLIB-CHAIN : "WindowsServer2008r2-000004.vmdk" : failed to open (The system cannot find the file specified).
2015-08-05T15:44:21.577Z| Worker#0| I120: DISKLIB-LIB : Failed to open 'WindowsServer2008r2-000004.vmdk' with flags 0xa The system cannot find the file specified (25).