Here's how I've got my setup on my 6700; maybe you can adapt it to your neeRAB:
I have the 'Work' connection setup to dial #777, use the standard username/password, and connect through the proxy wap.cricket.com:8080.
I have the 'My ISP' connection setup to dial #777, use the standard username/password, but it does not connect through a proxy. I have my MMS server configuration in ArcSoft set to use this connection specifically (not just internet, and not the 'Work' connection).
I know that we're both using different devices, but since we're both running Windows Mobile, I think there may be some relevance here.