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A quick note into AdWords support could solve this one pretty easily, but I'll give you a couple of high level guesses as well.
#1 there are keywords in the Ad Group which by themselves do not require review before they run, so they are active while the bulk of your terms await the editorial review. If 'widgets boom' requires review, it does not prevent your ad from being displayed on 'widgets pop'.
#2 there is also a small chance that for some reason one or two terms have been reviewed, while the rest remain unchecked. Unlikely, with the way our review system works, but anything can happen.