Hi,
after conversion there are leftover delta files from snapshot which are for some reason corrupted thus your VM cannot start. If the changes to the VM during the conversion were minimal you could throw away those changes in snapshot and try to boot VM from its parent disk.
To do this you must modify VM config file (vmx) and delete all references to existing delta files and point it to parent disk instead. You have to delete those delta files from datastore.
You can take this KB as reference:
You can achieve this also by editing VM config via client by removing all existing disks and add back those exiting parents..."RCSSRV02.vmdk" first try to delete all existing snapshots.
If the steps above are no applicable to you (you want to preserve existing snapshot) or you get stuck here or if it doesn't work please follow KB article below:
Sorry for limited info I am out of office and in time pressure...;)
Regards,
P.