Nevermind, you can write, just not save.
I assume they're using a latin-based field in their DB...
That could be the case. I often don't notice encoding issues until my colleagues complain their entries in Japanese are messed up.
This is one of the first things I test when I find a site like this. Most web developers don't seem to take into consideration things like character sets and encoding, yet they are so important.
Do you know if your input method produces unicode? That could be the difference.