I was having some gps accuracy problems on my jailboken phone so I decided to restore it. Before jailbreaking it again I tried the gps and it worked perfect. I jailbroken my phone and installed a couple of apps and when I tried using the gps it was really inaccurate again, i have no idea what the problem might be but it's evidently not a hardware issue. I saw some stuff about push and gps not working after an UNLOCK but mine isn't unlocked - and the push still works :s
I was running iOS 4.0.1 on my iPhone 4 Jailbroken and over the last two days (after I updated something on Cydia) I discovered that my GPS reception was very poor, and my accuracy was actually 63.5 miles. I decided to upgrade to iOS 4.1 and finally, everything was back to normal. I'm still missing my JB and I hope that the issue might be solved soon.