Why would mailtool pop-up a blank verification panel on message save?

[daniel.r.levy]

Mailtool (under SunOS 4.1.1 on a Sparc 2) has started to act odd on me
when I save a message to a folder file.  It beeps, then pops up a
verification panel that says nothing but "!" and shows a CONTINUE button.
When I mouse the CONTINUE button, the current message is saved in the
indicated folder file but nothing is printed about it and the current
message does not disappear.  It used to be that a message about the save
would be printed and the current message would disappear.  There's been
nothing in my .mailrc which would appear to cause this as far as I can
tell (here's what it looks like):

set alwaysusepopup
set bell=1
set noeditmessagewindow
set flash=1
set interval=120
set printmail=:
set trash=mai/garbage.can
set hold
set indentprefix="> "
set metoo
set mprefix="> "
set cmd=pg
set crt=22
set PAGER=pg
set prompt="mail> "
set quiet
set screen=22
set sendwait
set SHELL=ksh
set sign=" Dan Levy AT&T BTL Naperville IL (708) 979-2895"
set toplines=10
set lpr=Yes
set |=Yes

Thanks much for any expert (or otherwise!) advice on the matter.

Dan Levy                                                                 |
att[.att.com]!ihope!levy, levy at ihope.cnet.att.com                      --+--
For nothing worthy proving can be proven,/Nor yet disproven; wherefore   |
thou be wise,/Cleave ever to the sunnier side of doubt. -- Tennyson      |