The invite dialog if left unanswered will cause a disconnection from the IRC server due to time out. The client will not attempt a reconnect in the background. The status bar does update showing that you've timed out. Immediately after answering auto reconnect will kick in. This could be abused as a form of DoS for users who run 24/7 clients for things like logging or channel management.
I should point out this only effects the network the invite came from
SVN commit 988538 by psn: Change the invite dialog to non modal and handle all invites in the same dialog. BUG: 195396 M +2 -0 CMakeLists.txt A irc/invitedialog.cpp [License: GPL (v2/3)] A irc/invitedialog.h [License: GPL (v2/3)] A irc/invitedialog.ui M +9 -8 irc/server.cpp M +3 -0 irc/server.h WebSVN link: http://websvn.kde.org/?view=rev&revision=988538