I have an 8900 and i'm having real trouble turning on the wifi!!
I have already tried and failed with the following
alt shift del resets
full wipe of blackberry
browser settings changed to hotspot
deleting all saved wifi ssid's
The wifi did turn on very breifly and found my network but not anymore.
I just get the wifi tick box which won't go green and if i search for a network then it say turn on wifi which i try and do, then it comes back with unable to turn on wifi!!