Anyone out there have a problem with their GPS since they completed jailbreaking their iPhone 3G?

Before I did the jailbreak, GPS worked absolutely perfectly, down to following along in real time when driving. Last night, I commenced jailbreaking my iPhone (everything completed successfully, with no errors) and today, when attempting to use GPS, all I get is a very wide circle indicating that I'm in the Sydney CBD. Pre-jailbreak, it would pinpoint exactly where I was, down to which side of my office building I was in.

Has anyone experienced this issue? Better yet, does anyone know how to FIX it so it works the way it used to?

Many thanks in advance.