Users of the screen program will not be able to reattach older instances after upgrading to version 4.2.0; this is due to upstream having made a lot of changes to the internals, and switching from named pipes to sockets for communication. Please ensure your current screen instances are not anymore needed before upgrading.
screen-4.2.0 cannot reattach older instances
April 20, 2014 - Gaetan Bisson