I can't see how additional fonts will help. It's a Language issue (if that's the reason at all).
As you have a fairly decent grasp of English, I suggest you alter your Windows Language/Regional settings to English, install/extract GWX3.0 and then return to the Korean language pack.
If all of that fails, I suggest you double check the MD5 Hash codes for the downloaded GWX parts to ensure none are corrupted.
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