Looks like a compatibility issue. Either that app is not playing nice with another app you have installed (VERY tough to track down) or it's not working right with your BlackBerry.
You could try installing an older version of the app if you can find it.
You could try updating the OS on your BlackBerry. Latest 9780 OS
There are no guarantees the app will ever work for you. Some apps are poorly coded and cause some devices to gag like yours is doing. Often third-party apps are not well tested to function with a wide variety of other third-party apps installed. No developer can simulate all the conditions under which their app will be installed.