I attempted to install 10.5.5 on my 1st gen iMac G5 (upgrading from 10.5.4). The download seemed to go OK, then I clicked on Restart to install the update. Part way through, I got an error message, something like ( I didn't write it down exactly): "The update could not be completed because the install disc is damaged. Click here to terminate the update and restart your computer" So I did. Now, the computer hangs at a blue screen. I get (in order) the white Apple logo screen, then rotating star graphic, then dark blue screen, then light blue screen with cursor placed in upper left corner. Nothing after that. Any suggestions on what may be wrong or what to try?