This article is from the GNU Chess and XBoard FAQ, by Tim Mann email@example.com with numerous contributions by others.
After connecting to a chess server, XBoard 4.0.2 sends an escape
sequence to its terminal that is meant to display your handle and the
ICS host name (for example, "firstname.lastname@example.org") in the terminal's
banner and icon. It seems that several of the alternative X terminal
programs have a bug that makes them hang when sent this escape sequence.
You can work around the problem by using xterm, nxterm, rxvt, aterm,
xiterm, or gnome-terminal, all of which seem to work fine. In fact,
current versions of kterm and konsole seem to work fine too, so if you
are having problems with one of them, be sure you are not running an
Alternatively, you can disable this feature by commenting out the body
of DisplayIcsInteractionTitle in xboard.c and recompling xboard.