asterisk users - Jan 2010 - Asterisk 1.6.1.x SMDI MWI w/Fujitsu F9600 Problem

We have recently pulled an ancient Fujitsu-branded Centigram voicemail
system out of production use and replaced it with an Asterisk box, which
is now serving as our enterprise voicemail system and automated attendant.
The Asterisk system is connected to a Fujitsu F9600 PBX and uses the
1.6.1.x SMDI module to communicate between the two systems.

Save for one issue, the replacement of the old system has been a
resounding success. The issue is that the integration of the MWI (message
waiting indicator) functionality works, but only about 50% of the time.

The problem is easy to see, but hard to track. Sometimes when a message is
left on the voicemail system, the MWI will fail to show. Similarly,
sometimes after all messages have been reviewed, a lit MWI will fail to
turn off. Thus, it's not a problem specific to either the OP or RMV
parameter in the MWI message. Both work and fail with about the same
frequency.

I have put some logging commands into the SMDI code and thus have been
able to verify that Asterisk itself appears to be sending the proper codes
at the proper time, with 100% accuracy, best I can tell. As such, I don't
believe that this is an Asterisk-specific problem. However, I am wondering
if there could be an issue of interplay between the two systems.

If any of you are using an arrangement such as that described above and
have solved this issue, I would appreciate hearing the solution.
Similarly, if any of you have experience with SMDI and MWI and know of
potential glitches that I have not taken into account, I would appreciate
hearing about that as well.

Thanks for any insights any of you can provide.

- Will