dbgrid problem editing field

Hi, all

I have a simple DBGrid and the first column is an alphanumeric field with
the following EditMask

0000\-00000;0;_

When the user focused over the empty DBGrid and press any digit, a new
record is created and everything goes ok.  But when the first row is filled
and the user press TAB, a second record is created.  The user press, say,
the "1" digit and the field shows the following on the column:

11__-_____X, where X is the position where the cursor is placed.  As you can
see, the digit is duplicated, and by some unknown reason, the cursos is left
at the end of the editing mask.  The user must use backspace to go back and
then continue.

This happens on every record but the first.
I'm using Delphi 5 Ent Update 1, a Paradox table, cached updates enabled.
The only event on the grid is an OnColEnter which calculates a subtotal when
the user enter the 3rd. column.  I set a breakpoint in this event handler
and NO, it's not causing the problem.

Any ideas? Thanks...
Victor H. Ulloa.