Can't mount image

Hey guys,
I just sold my Mac Pro. I had an internal drive as a backup drive. To still access the data of the Mac Pro, I made an image of that disk and placed it on an external drive.

Now, when I want to mount this image from my MacBook Pro, it gives me an error message: "No activatable file systems" (or similar, I'm german...)
This is pretty crap because I need some files from there...

If I ask the disk utility, it says that the volume is damaged and needs to be repaired. But I can't repair it, the repair-button is greyed out...

The image is about 291GB big, maybe that causes problems...

Luckily I still have the HD laying around with all data on it, but I see no chance to plug it into the MBP. I'm currently building a whole PC (hackintosh) myself, that's why I sold the Mac Pro...

Thanks in advance!

 

Little update:
I installed the original HD on the MacBook where OS X 10.6.6 was still running
I tried to mount the image there, also no success.

Nobody able to help??