Whilst p2ving I came across this little issue when powering on a vm for the first time. I received an error stating the below:
Cannot power On: Reason: The parent virtual
disk has been modified since the child was
created. The content ID of the parent virtual disk
does not match the corresponding parent content
ID in the child.
Power On virtual machine
Now the only thing that I can guess happened here is that vDR created a snapshot of the vm as it was being created. The first thing I tried to resolve the issue was to right click the vm select snapshot and then consolidate. This then thew up another error message similar to the first so that was no good.
I deleted the snapshot and tried again but received again the above error message.
I googled around a bit and found some rather convuluted solutions to the problem however I decided on a much simplier solution that worked just as well.
Before performing any of the below ensure that you have deleted any snapshots that are active on the VM.
1: Right click the vm and select edit settings
2: Select the virtual hard disk and select remove but DO NOT delete the VMDK
3: OK your way out of the settings then go back into the edit settings menu
4: This time select Add and choose Hard Disk and use an existing virtual disk
5: Point your new hard disk at the VMDK file and click OK
6: Power on the VM and all should now be well.