I have seen a few of these when workign with clients and they can be a pain to get rid of.
before you try to remove the snapshot you will have to see that the VM is writing to as a HD. TO do this go to edit the VM and then select the first HD, look in the location section to see if it is using a file with a long 0000 or delta in the name. If it is then you must be carefull when removing it.
It could be many things causing the error and there are many ways to fix it depending on your VMware skill's, The simple way os to just clone the machine and then remove the old one!!!!
But if you like getting stuck in or do not have the storage for this them i would try the following.
ssh onto the ESX server.
login as root or SU -
browse to the VM directory using CD to the vmfs/volumes
create a snapshot first using command
vmware-cmd vmname.vmx createsnapshot snapts "troubleshooting 1 0" this will create a snapshot and sometimes can push the VMX back into life
let the snapshot compleate and you will see a new file called ......delta.vmdk
now to consolidate the snapshots use the command
vmware-cmd removesnapshots
When you are removing snapshots it can take HOURS for them to compleatly consolidate. the time taken depends on the VM and the ESX servers disk I/O's so wait for a good few hous checking the ...delta.vmdk files are decresing in size, you can do this via double clicking on the datastore the VM in stored on in the VI client.
Hope this helps, but if there are still problems then I think a clone will be the best way foward. Don't leave this too long as snapshots will grow and grow over time and if the datastore runs out of space your ESX server could crash, a snapshot file can grow to the size of its origonating disk.
