Another problem that may occur could be related to the root certificate in use by your organization. If it is self-signed, as opposed to a CA from a recognized authority (Thawte, Verisign, etc), you may have problems. You might try downloading the root cert and adding it to your device (sorry, I'm new to BlackBerrys so I'm not quite sure how this is done on a BB).
I do know that this problem affects pre-AKU2 WM5 Smartphones and iPhones.
Red BB Curve 8330m
v.4.5.138 (Platform 126.96.36.199)