I heard this phrase again today, so the message hasn't reached enough people. Here's the post I made earlier this month.
http://upgradeenglish.blogspot.com/2009/04/both-of-ok-is-not-ok.html
In addition to saying "both are OK", you can also say "both of them are OK". Both of these phrases are OK.
However, "both of OK" and "both OK" are both incorrect. Neither of them is OK. Don't use them!
Someone asked me "don't Americans always say 'both of OK'?" My answer was "NO! They don't! Only Japanese say that!" I think people are mishearing Americans who speak quickly. An American says "both are OK" quickly, and the sound of "are" becomes "of" in Japanese ears. The next time you watch an English movie or TV drama, pay close attention for this one.
