I guess you move from one connection to other instead of disconnecting from one network, and then connect to the new network. Yappari isn't too smart detecting networking changes (we'll fix that eventually). So if you want Yappari detect your 3G connection, disconnect from your current network. Wait like 1 second, and then connect to the 3G network. That will work. Do you have CSSU installed? Since CSSU has newer versions of Qt it usually fixes a lot of bugs people are having with Yappari. I really suggest to EVERYBODY to install CSSU.