If you need to revert a snapshot of a virtual machine (that is being backed up by a CBT-based backup application) to a snapshot older than its last incremental backup, you must do a full backup of that virtual machine before using incremental backups again.
This issue is resolved in vSphere 4.1 and vSphere 4.0 Update 3. Rather than potentially providing incomplete data, a change ID obtained before the snapshot revert is now correctly considered as being invalid.
To workaround this issue in earlier vSphere releases, perform a full virtual machine backup after a snapshot revert operation. If the backup application does not allow this as an option, you need to remove the CTK files for that virtual machine. The CTK files are stored with the virtual machine on the datastore and can be removed via the Datastore Browser. This delete operation can be safely done while the virtual machine is running.