Ok, so I'm trying not to use naughty words.

A user has sent me this backtrace from Emacs 20.2.89:

Signaling: (error "Invalid character: 4200, 4831827856, 0x0")
  insert("  €0    : ")
  (progn (insert (format "%c%c%c%s%5s: " gnus-tmp-marked-mark gnus-tmp-subscribed gnus-tmp-process-marked gnus-group-indentation gnus-tmp-number-of-unread)) (gnus-put-text-property (point) (progn ... ...) gnus-mouse-face-prop gnus-mouse-face) (insert gnus-tmp-grouplens "\n"))

[...]

  gnus-group-insert-group-line("dummy.group" 0 nil 0 nil)

What is happening here is that Gnus is trying to insert \200 into a
buffer, and Emacs (no longer) will let it.  What is now the proper
incantation?

It now does something like

(insert 128)

Is 

(insert ?\200) 

allowed?

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@ifi.uio.no * Lars Magne Ingebrigtsen