Have you had problems with the GPS on your iPhone?

I have been using runkeeper app for months with no problems. Suddenly the mileage recorder in it is going crazy. I traveled about 5 km and it said I had gone 166 km. I have googled and apparently mine is not an isolated problem but I could find no solutions. I downloaded another run tracking app and it did the same thing, also maps seems to be erratic. Just wondered if anyone else has had a similar problem and what you did. I hate giving it up for weeks while they send it back to Apple for repairs!