Button click event doesn't fire for iMode while using MMIT

[NIIT]

We are developing a mobile web based solution for Japan market that would be
accessible on iMode, Vodafone and AU/KDDI phones. We are using MMIT + Device
update 4.

The application is working fine on various simulators (iMode simulator
available from NTT Docomo site, J-Phone 919smu simulator, Openwave) but on
actual devices it works fine on Vodafone device but is not working on iMode &
AU devices. Following is what we get (On both devices):
1) Our first screen loads and displays properly.
2) User enters input values and submits the values; the application is not
able to proceed to next screen. The current page refreshes itself.
3) In the form tag, if we add action=â€somepage.aspxâ€, then the application
moves to somepage.aspx (we are using method=â€get†to support Vodafone)
4) Corresponding button click event in code behind is never fired when
working from these two devices (while it fires while working from Vodafone
device)
5) We tried by changing from Get to Post method but the situation is still
same.
6) We have tried by disabling “view state†& “session state†(we are using
SQL Server session state), but with no luck.
7) In web.config, we already have useFullyQualifiedRedirectUrl="true"

Any suggestion would be welcome.