Two things. If your using a VPN the Blackberry may not support the required xxx8220;keep alivexxx8221; packets needed to keep the tunnel open and the connection dropps.
The Second issue may be the security used on the access point vs. the device accessing. The new devices use various improved methods that the old WIFI modems did not. I cannot find any indication the Blackberry uses any security method except Wired Equivalent Privacy (WEP) security.
If you are using the Push Button Setup method for Wi-Fi, verify that the network
access point is enabled with Wi-Fi Protected Setupxxx8482;, and that it has been set to
send its profile. The Blackberry needs to xxx8220;seexxx8221; the network
some additional Information you may want to read from RIM. View Document