Class not found Exception for Nokia 6230i

[Debojit Nag]

Hi all
I am getting a class not found Exception for Nokia 6230i for the following line using WMA API:
MessageConnection conn = (MessageConnection) Connector.open(addr);

This is a part of my code for sending SMS through Nokia 6230i. But this code runs fine with default emulator or with Sony Ericsion.So, what is the source of exception and how this could be handled?

Thanks in advance.
Debojit