I was using Liberty ROM (android 2.3.3) on my Droid X and Vietnamese looks broken (all the diacritical marks are mixed up: acute become grave the press goes above the character instead of below), while the same characters displayed just fine on another phone.
I tried to install the new Roboto font from Android 4.0 via ROM Toolbox but it doesn’t fix the problem.
So I tried to copy the fonts from my other phone running Android 2.3.5 and now everything’s fine. Extract the font file, mount / as writable in ES File Explorer, copy the files to /system/fonts and you are set 🙂
Here are the font files (I guess they are free to distribute since they comes from AOSP)