have you had your sim card a long time?
i only ask because every year i would upgrade my phone with o2 and just swap the simcard to my new phone, when i first got my
n95 8gb i did the same thing.
my gps was patchy and took ages to connect, i thought this was the norm, then i noticed my daughters sim card actuly had GPRS on the back but mine didnt, so i contacted 02 and requested a new sim.
the new one has the GPRS in the code on the back and now the gps function is brilliant.
it locks on almost instantly and keeps the signal better, browsing is also faster :)