I have just downloaded the latest update ( 10.5.5 ) and then rebooted my iMac , next the software Update box appeared on screen as usual, saying .. Installing 1 item , configuring Installation . Then the Blue progress bar started to move to the right , went about 1/4 of an inch and stopped there, I left the iMac running for Two hours and the progress blue bar had not moved. I then turned off the iMac , re booted , re connected to the internet , clicked software up date, the 10.5.5 update was shown again, I then clicked to download this update, then the do you want to shutdown now notice appeared, so I shutdown again and the whole same process started again as before . So basically It seems that the update 10.5.5 has been downloaded onto my iMac, but gets stuck on the .. Installing 1 item - configuring Installation part. I have gone through the Zap PRAM and Repair Permission , but that seems not to have resolved any thing I did un plug any external USB items while the , Installing 1 item - configuring Installation part was in operation. Other that that the iMac is running fine. I am still in a learning Apple Mac mode, so any help would be most appreciated.