Viewing pda .net website on a blackberry connect handset

Hi all and happy new year, hope everyone had a good time off work!!

I have a problem, we have created a .net web application aimed at
pda's using Windows Mobile 5 and above and it works great. Now that
we have expanded to pda's my boss also wants it too work on a
blackberry handset as well. Viewing the login page of the website
renders correctly, but after entering the username and password and
pressing Ok, the login page just reappears instead of redirecting to
the home page as it does usually on any windows based pda.

I have looked at the setting within the browser and Java/ECMA script
is enabled and it also allows cookies.

Does anyone have any ideas?