Some users of the iPhone Runkeeper app on iOS4 (on IPhone 3G/3GS/4) seem to be struggling to get it working properly.
Here are some handy hints:
* app crashes on start – delete and reinstall app via iTunes
* not able to get GPS fix – check that you have Runkeeper enabled in Location Services (Settings>General>Location Services>Runkeeper), make sure Airplane mode is OFF, turn off Wifi
* poor performance when using app with multi-tasking – make sure any unnecessary apps running in background are closed (double tap home button, select app and hold until app icon jiggles, then tap X). There is an update in Apple’s approval queue which is going to improve multitasking on iPhone 3GS/4
* activity stats not uploaded to Runkeeper.com at end of activity – check that you have correct username/password combo
Hope they help.