I have a Canon MP610 multifunction printer USB cabled to an iMac running 10.8.2. Every time I turn the printer on, a dialog is displayed on the iMac saying 'Would you like to download and install software for "Canon MP610 series"? Not Now or Install'

Interesting. No driver updates available in the App Store as I would now expect. Anyway, what with the recent update to Mountain Lion, it all seems reasonable and I click Install, perhaps foolishly, and a search for updates commences. A package appears to start downloading with a progress bar progressing. This soon stops and the message :

"The software is currently unavailable. You can check for software later by choosing Software Update from the Apple menu"

is displayed. Huh? I can dismiss all the dialogs and the printer continues to operate normally. I suppose I can leave the printer turned on but it's a nuisance and it's making me nervous! Can anyone tell me what's (not) going on?

Andy