Input inconsistency between edit boxes in dialog forms

[infandibulum]

Hello,
I'm developing using Visual C++ 6.0 on a Windows 2000 PC.
I'm experiencing some very subtle inconsistency between edit
boxes on different dialogs and would appreciate any
suggestions as to how to unravel the situation.
The edit boxes are for numeric input and have identical
properties set. They both have upper and lower bounds set.
The dialog boxes they are part of are property pages on a
property sheet containing 6 property pages. All of the
pages have the same properties set. Two of them are
functioning just fine, but the other four are not.
When entering a number that is out of the accepted range
for the box, the two pages/edit boxes that work do the
expected -
entering a number out of range and hitting "ENTER" gives
no response. Hitting "TAB" brings up the error dialog
telling the user the correct range for that field. Hitting
ENTER or clicking on that error dialog removes it and
re-entering a valid value is the only way to move on. This
is fine.
On the screens that are lame, the ENTER key, somehow,
stays "active" when the number entered is out of range.
If I hit ENTER when the error dialog box (with range info)
comes up, a handler for another button on the page is
executed (!?!). How do I track down what is different
between the pages? Everything seems to have the same
properties set. Using the mouse has the same problem as
the ENTER key on theses pages.
It is apparent that I can keep the focus on the edit
box, where it belongs until a correct value is entered,
on two pages but not on the other four.
All six pages are initialized and activated the same
way.

Thanks in advance.