Comment 2 for bug 11334

I believe the reporter has just discovered how X's clipboard mechanism works;
there is no persistent store. When you click 'copy', the source window simply
announces that it is claiming the CLIPBOARD selection (others to claim include
PRIMARY and SECONDARY). When you click 'paste', that window is queried for the
contents of the selection. If the window[0] does not exist, it cannot be
queried, and thus you cannot paste.

[0]: Not window as such, but connection to the X server. As soon as that
instance has no connection, it's out.