Hmm, I think one workaround is to click the 'Connect to the Internet' button, rather than the 'Login' button, and submitting credentials on the form on the page that follows seems to work with the stock n900 browser.

Funny thing, the secondary page seems to give a javascript error on the n810 MicroB browser (running most recent Diablo release).that the first page raised for the n900 browser :-/