From Wifi / UMA Error Codes - BlackBerryFAQ
W006.1 - ISP or T-Mobile network error.
Meaning: The phone is unable to establish network connectivity: This could be a problem on the ISP side or the network side.
1. The connection to the WAN port of the wireless router is down: either the cable is unplugged or the DSL/Cable modem (whichever applies) is turned off. This could also be caused by an outage of the DSL/Cable service.
2. Check if MAC filtering is enabled on the wireless router. If it is, check that the phone MAC address is on the Safe List, if not, add it.
3. The network that the user is trying to connect to uses Web Redirection: this means that when trying to connect to the network in question with a laptop, you are required to enter username and password or pay to use the service. The phone cannot connect to such networks.
4. IPSec is not enabled on the router you are trying to use. Enable it in the router settings and try again.
5. The problem can be caused by network issues. At this point, the user might want to try at a later time.