It looks like Foursquare is in the bug squashing game with their latest BlackBerry app Alpha build. My guess is these builds are still fixing issues with previous releases. We actually had a reader brick their device with a previous Alpha build so downloaders beware! On the other hand I just installed it on my BlackBerry Torch and everything is dandy.
You can pick up v1.9.72 Alpha of Foursquare at www.foursquare.com/blackberry/alpha/