The v22 of Android.Support.v7.AppCompat has a change that will result in (shortly said) losing your drawable background on your button for gingerbread.
I've discovered this today and it's already been reported, see issue: https://code.google.com/p/android/issues/detail?id=160591
Also on JellyBean the (left-)padding is different/lost.
I downgraded my package to v18.104.22.168 and it's working again.
Just want to inform you to help saving you hours of searching, which I did today.