One of the relevent portions I found in that log:
Entering onWindowReactivate()
Window reactivating...
Leaving onWindowReactivate() - return
Entering GameConnection::setLagIcon(10773, true)
Leaving GameConnection::setLagIcon() - return
Connection with server lost.
Entering GameConnection::onConnectionDropped(10773, TimedOut)
You timed out after reactivating the window. However, between there, your computer was able to display the lag icon. This makes me think that it doesn't have to do with your Blockland program hanging up, but it could be anything else. Make sure that all of your drivers (video, network, etc) are up-to-date.