Check your settings in Settings -> Location and security
. If you have a data plan, I'd suggest enabling Use wireless networks
, Use GPS satellites
and Use sensor aiding
for the fastest possible location fix. If you don't want GPS to use your mobile data, deselect Use wireless networks
.
Also, you could see what goes on with the GPS with GPS Test (https://market.android.com/details?id=com.chartcross.gpstest).
Does the GPS icon start blinking in the notification bar when some program attempts to use the GPS?