Actually, it's not an MDS ony app. I know a number of people who have it working with just the standard browser, including myself. It is set to launch the default browser. Perhaps someone more familiar with Blackberry configuration could help here?
Are you using a Nextel BB? I seem to run into a problem when 411 tries to find the information using the NOL browser - which I believe is WAP only.
If I could figure out to make Reqwireless the default browser, perhaps I wouldn't have any problems.