This is probably memory corruption, either due to a byte compiler
bug
(not reserving enough space) or a bug in memory management.
Gnus byte-compiles code on the fly if 'gnus-use-byte-compile' is set to
something else than nil, and it used to be incompatible with xemacs. But
I made sure that this feature is never used. So there is something else.
Do you think running xemacs under boundschecker might help in identifying
the problem? I'll see if I can spend some time on it (afraid it can be
tricky, and the bug occurs at random).
Fabrice