Re: X protocol error:

[Richard Stallman]

    It means that somewhere you (or someone else) gave Emacs a font name that 
does
    not exist on your system.

Emacs should not die just because someone specifies a nonexistent font
name.  It should detect that error, report it cleanly to the user, and
carry on.

If someone can figure out which part of Emacs sends the X command
that gets this error, we can implement that error checking.

So please see what etc/DEBUG says about debugging X protocol errors.