NWIDir search results not reliable

I have a program written in VB6 that uses the NWIDir ActiveX control to generate
a list of all of our student and employee accounts.  This program has been
running fine for the past 6 years, however within about the past month, the
NWIDir control has not been returning all of the user objects in our eDirectory
tree reliably.  We have about 107,000 user objects in our tree but the control
may randomly return only a fraction of that number.  The odd thing about this
issue is that no errors are returned when the control returns in incomplete
search result, and the truncated search result can't be reliably reproduced. 
It's critical that the user lists be properly generated, because we are using
them to feed other systems.   Has anyone experienced anything like this and if
so what steps did you take to resolve it.  Thanks in Advance.

After experimenting for a few days, I have discovered that when trying to search
the entire tree for all users, eDirectory times out and only a partial result
set is returned to the NWIDir control.  The NWIDir control has no clue that
there was an incomplete result set returned by the search.  The solution is to
search for CN's beginning with each letter of the alphabet separately.  This
drastically reduces the number of entries returned from eDirectory in any given
search and reduced the run time for my application from 2 1/2 hours to under 30
minutes.  It seems that eDirectory is able to respond much quicker to an LDAP
query if the number of entries returned is smaller.