Okay, so your backup, does 3 things, backs up something on c, exchange state, data (h drive?)...
First thing I see, is that it happens in the morning, when users are working, can you change this to say, 1 in the morning?
Next, I would break this down to 3 jobs, not one. Will also make troubleshooting easier.
1. Backup data first, overwrite tape.
2. Backup exchange, append to tape, schedule 3 hours after the first job, and terminate if it can't append.
3. Backup whatever files on c you want, schedule 3.5 hours after the first job, and terminate if it can't append. Also, do you really need anything off the c drive? Typically if a server or backup pc fails, I reload the os from scratch, create users/domain, then restore the data.
Do that, and then see which job fails.
Also, I don't know if this is the cause, but it doesn't like the following paths...
\NET_DATA\SHARE\David
\NET_DATA\SHARE\Ron Webster
Matt J.
Please always take the time to backup any and all data before performing any actions suggested for ANY problem, regardless of how minor a change it might seem. Also test the backup to make sure it is intact.