I have a wifi network at home and work. Every time I leave either wifi and switch over to my mobile provider (Bell/BES), the blackberry connection is lost. I always have to go to Manage Connections and turn the mobile network connection off/on. Both wifi connections have the option set for inter-access point handover. Running 6.0 bundle 2718.
What gives? This hasn't always been happening with this wifi/network set-up, it only started about 3 months ago.
This has happened to me on my Bold 9900. Then I upgrade to a leaked OS which solved the issues for me. I think this is caused by the OS so may be you want to either downgrade or upgrade your OS and see what happen.
On my Bold 9700 I even used to have this issue where with full bars I couldn't get a call connected. Again an OS upgrade solve the issue for me.