Please try restoring directly to the Exchange 2007 Recovery Storage Group. After creating the proper database within the Recovery Storage Group, make sure it's dismounted and marked for overwrite.
Next, make sure the destination folder exists, and that it is empty.
Finally, run the restore in UltraBac, making sure to restore both the desired database and the Log Files.
After the restore you should be able to mount without an issue.
Note that if your backup server and Exchange server are two different machines, you will likely have to run the restore locally on your Exchange server.
If you have any additional questions or issues, we will be better able to assist you if you call in, 425.644.6000.