Basically as the title says, despite having updates available (the new iTunes at minimum), and the app store badge having a number of updates shown, the updates page takes an age to load and then eventually shows no updates available. Any ideas?
Like Software Update before it, the Mac App Store in Mountain Lion has various caches that are supposed to speed it up. However, sometimes these get corrupted, making it slower instead of faster. If this is happening to you, deleting the Mac App Store's caches will fix it. The tricky part is finding them, though - one is in ~/Library/Caches, and another one lives in a subfolder of /var/folders (took me some searching to track that one down). Both of these locations are hidden in the Finder, making getting to them awkward.
Generally speaking, yes - but I have not used OnyX in quite a while. I do not know if it handles the MAS.Does a program like Onyx make finding and clearing the catches easier? I'm usually scared to use that program too much but in this case I might give it a go.