First make sure you are using the 4.5 OS and not 4.3. If you are using 4.5 then you must turn on your GPS by going to OPTIONS>ADVANCED OPTIONS>GPS>GPS SERVICES>LOCATION ON.

The Curves GPS is only unlocked for BB maps and is locked for third party apps. If you use it on google maps for instance it will only do tower triangulation and wont do turn based navigation.

The TOUR and Storm both have autonomous GPS which can be used on third party apps.

So if you want to use GPS on your curve turn it on and use blackberry maps. It works great I used it all the time when I traveled.