12.04 upgrade problem

[Jim Smith]

I upgraded to 12.04 from 11.10 and rendered my system unbootable. I can 
boot a 12.04 CD and mount my Linux Partition. Having done that I would 
like to transfer my important files to an external hard drive so that I 
can re-install from CD. I can mount the partition and go to the "home" 
directory, but I'm not allowed to enter my personal directory. Any way I 
can force this?

Thanks

Jim