Myself and my manager just revisited this issue, and we came up with what was wrong.
When using a Japanese operation system, the browser itself has a Language Preference. This can be accessed by:
Tools > Internet Options > Languages
For US Windows machines (for IE), the one that shows up is en-us. The problem is that for Japanese Windows, the one that shows up is ja. So no matter what you specify in the meta tag for charset, the editor won't recognize it and always garble the Japanese text. By adding the "en-us" Language to this box in Japanese Windows, it allows the editor to recognize the Japanese characters.
The charset used was windows-1252.