According to that it has nothing to do with a bug in Lion. Try starting up off your original disc and repairing your hard drive. Zero out all sectors if necessary and then install. If your disk keeps failing to mount, I would suspect the drive has failed. Maybe DiskWarrior or TechTools can repair it.
When I try my orginal disks it will not work because I upgraded to Loin. I have downloaded the drive for Loin and that is what I have been using to try this.
Its not the hard drive because it is working just fin for me now. Searching the web it appears many people are all having the same problem, but no solution.