Currently Being ModeratedSep 13, 2013 2:35 PM (in response to brittnitt)
The disk is likely dirty, use a bit of rubbing alcohol and a very soft clean cloth to polish.
Another possiblity is the disk is defective or the lense on your Superdrive is dirty.
It also could be that Mac needs a 10.6.3-10.6.8 machine specific copy of OS X with drivers not on the 10.6.3 disk.
Call Apple to order.
Currently Being ModeratedSep 13, 2013 3:21 PM (in response to ds store)
Thanks for the suggestions! I ended up just shutting it down, rebooting it while holding down the alt key, ejecting the disk, then reinserting it. Somehow that worked! Installation success!