How can I get my iPhone to display Hangul (Korean alphabet) characters in text messages I receive?

I used to receive Korean texts with the Hangul characters showing up, no problem, but now since I updated my iPhone on 11/24/10 the hangul characters in my texts are not being displayed, its an iphone 3g. Am I better off just restoring my phone back to when the characters were displayed or trying to find a solution to this problem?