Hi Linc - I've been having this failed updates problem for several months as well. The task of tracking down individual downloads every week or two to stay up-to-date is frustrating. Per these instructions, I'm pasting the end of log messages from today below:
Jan 8 13:56:56 NAME-OF-MAC.local Software Update[325]: Acquired Lock: 504, 838, 0
Jan 8 13:56:56 NAME-OF-MAC.local Software Update[325]: Releasing Lock: 504, 838, 0
Jan 8 13:56:56 NAME-OF-MAC.local Software Update[838]: SoftwareUpdate: elapsed scan time = 21.5
Jan 8 13:56:56 NAME-OF-MAC.local Software Update[838]: SUAppStoreUpdateController: scan (f=0, c=1, p=1, r=1) found 041-8081, 041-9137, zzzz041-8972
Jan 8 13:56:56 NAME-OF-MAC.local Software Update[325]: Acquired Lock: 504, 838, 0
Jan 8 13:56:56 NAME-OF-MAC.local Software Update[838]: SUAppStoreUpdateController: session began for products 041-8081, 041-9137, zzzz041-8972
Jan 8 13:57:56 NAME-OF-MAC.local Software Update[838]: Could not download package at URL http://swcdn.apple.com/content/downloads/53/02/041-8081/jex01nudh37t8cusghkiy1ek i5crm76f4b/Safari6.0.2Mountain.pkg - invalidating and will try again
Jan 8 13:57:56 NAME-OF-MAC.local Software Update[838]: Product 041-8081: no package found for identifier com.apple.pkg.Safari6.0.2Mountain
Jan 8 13:57:56 NAME-OF-MAC.local Software Update[838]: SUAppStoreUpdateController: error downloading product 041-8081: Software Update can’t connect to the update server. Make sure you’re connected to the Internet, and then try again.
Jan 8 13:57:56 NAME-OF-MAC.local Software Update[838]: Product 041-8081: no package found for identifier com.apple.pkg.Safari6.0.2Mountain
Jan 8 13:58:26 --- last message repeated 1 time ---
Jan 8 13:58:57 NAME-OF-MAC.local Software Update[838]: Could not download package at URL http://swcdn.apple.com/content/downloads/09/30/041-9137/izc98a9ineshckm7m84x5kyv j0mufsx131/RAWCameraUpdate4.pkg - invalidating and will try again
Jan 8 13:58:57 NAME-OF-MAC.local Software Update[838]: Product 041-9137: no package found for identifier com.apple.pkg.RAWCameraUpdate4
Jan 8 13:58:57 NAME-OF-MAC.local Software Update[838]: SUAppStoreUpdateController: error downloading product 041-9137: Software Update can’t connect to the update server. Make sure you’re connected to the Internet, and then try again.
Jan 8 13:58:57 NAME-OF-MAC.local Software Update[838]: Product 041-9137: no package found for identifier com.apple.pkg.RAWCameraUpdate4
Jan 8 13:59:27 --- last message repeated 1 time ---
Jan 8 13:59:57 NAME-OF-MAC.local Software Update[838]: Could not download package at URL http://swcdn.apple.com/content/downloads/56/42/zzzz041-8972/kklo27b5gf5fqxsfmmir i7ove3n742dj3c/MobileDevice.pkg - invalidating and will try again
Jan 8 13:59:57 NAME-OF-MAC.local Software Update[838]: Product zzzz041-8972: no package found for identifier amds
Jan 8 13:59:57 NAME-OF-MAC.local Software Update[838]: SUAppStoreUpdateController: error downloading product zzzz041-8972: Software Update can’t connect to the update server. Make sure you’re connected to the Internet, and then try again.
Jan 8 13:59:57 NAME-OF-MAC.local Software Update[838]: Product zzzz041-8972: no package found for identifier amds
Jan 8 13:59:57 --- last message repeated 1 time ---
Jan 8 13:59:57 NAME-OF-MAC.local Software Update[325]: Releasing Lock: 504, 838, 0
Jan 8 13:59:57 NAME-OF-MAC.local Software Update[838]: SUAppStoreUpdateController: session ended for products 041-8081, 041-9137, zzzz041-8972