ExFAT formated harddrive won't mount on Macbook Pro

My job recently gave me a 4tb G-Tech G-Drive to access video and audio files to edit. The drive works fines on my bosses Windows computer and the drive is formatted for exFAT but it won't mount on my Macbook Pro. My OSX is 10.8.4 and the drive appears in the disk ulities and when I try to repair, it says this:

Verify and Repair volume “disk2s1”

Checking file systemChecking volume.

Checking main boot region.

Main boot region is invalid. Trying alternate boot region.

Checking alternate boot region.

Alternate boot region is invalid.

The volume could not be verified completely.

Volume repair complete.Updating boot support partitions for the volume as required.

Error: Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.

I don't have the option to reformat as this is a work external and I don't want to do anything that will erase the files and I also don't have access to the windows computer. Is there a way to access the files or fix this or will I have to go through the long process of giving the hard drive back to my boss and waiting for him to reformat the drive and giving it back? And if he does give it back and the same problem happens, how can I fix this? I read about cluster sizes above 1024 Mac OSX doesn't read it, is this true ? I really need to fix this.