There is a problem with web-box from PDA. The "OK" button does not work in the web browser of Internet explorer or PocketPC. I can login and monitor it from the web-box but cannot add or modify any entry.
What version of the RotuerOS is installed on your router ?
I have tried with Windows Mobile 5.0 and provided Internet exploler with Webbox, it worked some time ago. I will try to test this again with the latest version, however in my opinion webbox is more designed for monitoring not configuration.