There could be a number of reasons why hash numbers don't match you attempt to restore the image to another hard drive.   One major reason is bad sectors on drive.   Watch the dmesg output or read the /var/log/messages file to see if the following errors occur:

kernel: hdX: read_intr: error=0x40 { UncorrectableError }, LBAsect=98823, sector=98759

You should also verify your image when you acquire it.   Make sure the hashes match when you acquire the image.

I am not sure if VMWare could be part of the issue, especially if you are imaging a VmWare disk.   Even if you are booting from a Helix CD in VmWare, I am not sure if something else isn't writing to the vmdk files. 

The point is, that there are many things that can go wrong.  Maybe we can help you pin point the issue.   What is the exact configuration you are using?   What drive types and makes, external USB to IDE/SATA connectors, and other devices are you using?  What is your procedure?   What do adepto logs say?

BTW, all of the above should be going into your case log as you are doing an investigation.  Some of the information should go onto an Acquisition Document.