asterisk users - Jun 2005 - Issue with Not Capturing All Key Presses

In our IVR we have a user enter a 6 digit number and information if
returned.  Our problem is that no all of the digits that the user
presses are being recevied correctly.  Its not as if the first digits
are being cut off or the last, its just some digits aren't coming
through.

Our setup is that we have an IAX channel coming in from VoicePulse
going to our Asterisk box via the T1 coming in to the office.  This
line is shared somewhat but we would expect to have more than enough
bandwidth to handle 1 call (still testing) at a time.  Does anyone
have any suggestions on how to test where the bottleneck (or other
asterisk issue) might be?

Thanks,
Michael