Edit field on Active X Control problem

I have an Active X control with edit fields on it. When the control is loaded into Internet Explorer (5 or greater) on Winnt 4.0 machine, it does not allow the user to type anything into the edit fields. This only happens on Winnt 4. Now for the hard part; this doesn’t happen on all winnt 4 machines, and sometimes, it just stops working on some machines that had previously worked. Sometimes, installing a newer service pack will fix this, but not every time. Short of forcing the client to update to Windows 2k, I’m all ears.