keyboard lag / backspace problems

for your information i am studying at japan so i set my iphones keyboard to english and japanese keyboard.
but after i upgraded my iphone to version 3.0os, i having problems with the keyboard lag and also backspace problems.
i have followed the instruction regarding this problem but until now i still having the same problem.
is it because i am using japanese keyboard?
anyone know about that?i really need help.

anyway this application is really great.

toyama about Jelly SMS