Similar to bug #339556, if the update process is displaying a list of change logs that is long enough to require the pager, then synaptic will appear hang indefinitely unless the user expands the Details section and pages through the messages. There's no indication that this is necessary: in fact, the displayed message is "The marked changes are now being applied. This can take some time. Please wait." There is no indication to the user that they need to stop waiting and acknowledge something before the update can continue.