Double checked and indeed, for the pre-3850 build plist, it did not have a "Check for Updates" boolean at all, even though it was manually set to not-check for updates and in shows that in the UI when I open up the prefs in Quicksilver to check.
I copy and pasted the boolean from a new plist into the old plist. Hopefully that should fix things. Thanks Patrick, hopes this thread helps for anyone else that encounters the same problem!
