UPDATE: Well crap... I just had the ABC-disabled glitch happen to me out of the blue today, and no explanation why. I'm going to reapply the tweaks to get it working again and then I'll be doing some registry monitoring to see what the heck is changing to trigger this behavior.
UPDATE 2: Well, as I suspected, something was changed, and
MakuSoto discovered it too. Apparently, the ABC/T9 toggle is getting switched somehow, and although I'm not sure how yet, at least I know what to watch for.
UPDATE 3: I am updating the cab file in the original post above with the appropriate tweak by MakuSuto.