GRT restores of Exchange 2003/2007 fails with error:
Final error: 0xe000ff12 - A communication failure has occurred with an Exchange Store resource.
Final error category: Resource Errors
V-79-57344-65298 - The Exchange Store service is not responding. Backup set cancelled.
Connection to the restore target has been lost. Operation canceled.
The above mentioned error occurs if the restore is done from a corrupt backup set.
Try restoring from a different backup set.
Make sure that the backup set does not have any red X (failed job).