I have an HTC 6800 and have experienced a similar problem.  I cannot at the
moment produce an instanced of where this occurs other than at the Wall
Street Journal site where I have to put in a username and password and then
receive an OK to proceed and am presented with a Continue button that
doesn't work.  To get to see the site, I have to go to the home page again
and then can see everything since my username and password were recorded
earlier and a cookie was set.

I think it may have to do with the button using Java to an extent greater
than the Windows Mobile browser has the ability to understand.  There are
other items that the browsers supplied with Win Mobile won't render.  An
IFrame comes to mind as one.