We had a bit of weird issue recently where DPM would not even start a Tape Backup and errored out with the following “RA cannot read from/write to temp area. (ID 30107 Details: The system cannot find the path specified (0x80070003))”
To fix this we had to create a folder called MTA in the below location, obviously path may be a tad different in your environment.
D:Program FilesMicrosoft System Center 2012DPMDPMTemp
As soon as we created the folder all started working J