I don't get it. That's a new one on me. How did you fix it, change permissions?
Regarding your install DVD problem. Reboot the machine then see if the DVD works. If not, try rebooting again, and quickly popping the DVD in after it chimes, then hold the C key down to try and boot from the DVD, in case something is fubar with the system preventing the DVD from showing up.
Do any DVDs or CDs work?
Edit - I'll check back later, gotta run for an hour or so.