Have you tried plugging the bridge into the Vista machine to see if it works there? Just to tell if it's settings maybe wrong in the bridge or if settings with MorphOS.
Don't get mad for asking what may be a dumb question, but you of course logged into the bridge already from a browser on the computer that the bridge is plugged into, using it's IP address in the URL area- 192.168.1.226 ( the user name is probable blank and password is 'admin' on that thing) and configured it to connect to your Wireless modem with any WEP or WAP passwords if you use them?