The App Store is sure to have its share of bugs, in fact, here’s one time-consuming App Store-update bug that could lead to severe frustration. Some users are logging into the iTunes Store to download app updates to find that they have an "outstanding balance." This predicament could leave users with buggy, partially downloaded software or just won't allow you to download the updates at all.
Fear not, it is probable that there is no outstanding balance (unless you're purposely trying to cheat the system). It seems the iTunes App Store belives you're trying to download applications without adequate credit available on your credit card when you select "Download All Free Updates." Downloading each App update, one at a time, should remedy the situation.
The idea behind the iTunes credit hold is tp keep users from downloading beyond their credit’s spending limit, but the bug can be annoying for users who just need their App updates.