It's not totally clear where this bug comes from.
Without version info from xterm and source code (or at least debugging symbols), chances are I won't be able to root cause this one.
At some recent debian upgrade (I just did a big one to 3.1) I found a segfault bug in xterm. Not sure what the version is, but it might be "200"
% xterm -version XTerm(200)
Reproduction is easy.
strace claims that it segfaults right after attempt a failed read on file descriptor 5. Who knows..
Don't even know who to report this bug to.