If your BlackBerry is stalling or freezing whenever you click "Check In," there's a way to fix that! Old versions of BBM can cause the app to freeze. Upgrade BBM, uninstall Foursquare, and do a battery pull. Once all that is done, reinstall Foursquare from https://foursquare.com/blackberry/beta or from App World.

If you can't navigate or use your phone at all because you clicked "Deny" when Foursquare opened, just download BlackBerry Desktop Software onto your computer, connect your BlackBerry to your computer, and force uninstall Foursquare.