Have 10.6.8, 4 gigs ram. Dl'd and ran Lion install rebooted to message that hard drive was damaged and could not be repaired. Now cannot reboot my machine without that message. Put my original snow leopard in drive but can't get anywhere. Also, I cannot hit the continue or any button with my trackpad.
Lion is now installed on my machine. Two previous failed installations. After each failed installation I ran disk verify from the original sl disk in the cd drive. I had to erase and reformat the drive and restore from time machine.
The successful installation: I ran disk verify before the lion install and from the cd. No errors. But then I also ran permissions verify and repaired any issues. Then I re downloaded and installed Lion with success.
There had been no reported permissions issue previously but verify found issues. Don't know if this is the issue on my machine but fixing it preceded the successful installation of Lion. Perhaps it will help some one else.