asterisk users - May 2004 - No stutter MWI on zaptel channel with message waiting

This one is making me crazy. I have a T1 connection from * to an adit
channel bank. When there is voicemail, there is not stutter for message
waiting indicator. Here is zapata.conf.  

Thanks!

[channels]
language=en
signalling=fxo_ks
rxwink=300

usecallerid=yes
hidecallerid=no
callwaiting=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
cancallforward=yes
callreturn=yes

; spans one and two connect to the Adit 600 channel bank
signalling=fxo_ks
group=1
context=inside
channel => 1-48

callgroup=1
pickupgroup=1
callerid="Paul Mahler" <100>
context=inside
mailbox=100@inside
channel => 1