If the network is lost while a 'choice window' like "Clear Conversation" is open... you're lost. The phone will not do anything before you 'dismiss' the "Network Lost" popup notification. (Meaning: the downmost two big buttons do not work). However you cannot do that, because that popupnotification is 'hidden away under' the now non-operational choice window! Catch-22.

You cannot even shut off the phone normally. Because if you press the 'off' button for a while, the "slide to turn off" slider appears... but also, like the 'choice window', does not respond to input. *sigh*.