This is a known bug in the Ultrix version of the Xlib library which
applications use to get access to the X protocol. It exists in Ultrix 4.0
and 4.1 and possibly later versions as well. This ISN'T a MacX bug; it
happens under similar circumstances with Sun and other 68K-based X servers.
MacX seems to have the problem more often than other servers due to the
built-in conversion of the Clipboard to Macintosh Clipboard; this
aggravates the problem.