It seems to be working ok mine. Have you tried closing the iPlayer Radio app via your iPad's multitasking bar and seeing if it works when you re-open it ? Double-click the home button to open the taskbar, and then swipe or drag the iPlayer Radio app's screen from there up and off the top of the screen to close it, and click the home button to close the taskbar.
If that doesn't fix it then you could try a soft-reset : press and hold both the sleep and home buttons for about 10 to 15 seconds (ignore the red slider), after which the Apple logo should appear - you won't lose any content, it's the iPad equivalent of a reboot.
If that doesn't work either then you could try deleting the app and redownload it via the Purchased tab in the App Store app
