Cancelling Xgrass windows

I'm having problems with the 'cancel' button which is available with most of
the text windows which Xgrass produces. This option clears the contents but
does not close the window. Worse, it subsequently prevents me doing a manual
close from within the mwm menu. My first problem is presumably to discover
whether this is a quirk of our system (HP 9000-750; UX 8.0; X11R4; no Ansi).
Can anyone give some general pointers to what I should be looking for? (I have
minimal X knowledge). I presume that code for the cancel button is nicely
encapsulated somewhere. How do I find it?

--
Conn V Copas
Loughborough University of Technology tel : +44 509 263171 ext 4164
Computer-Human Interaction Research Centre fax : +44 509 610815
Leicestershire LE11 3TU e-mail - (Janet):C.V.Copas@uk.ac.lut
G Britain (Internet):C.V.Copas@lut.ac.uk

I have the same problem on my HP9000/720 ; HPUX 8.07. Any suggestions?

Bob Courtney
Atlantic Geoscience Centre
Bedford Institute of Oceanography