>>Dmitry,
>>Probably a keypress code is in effect. I'd try like this for a quick check :
>>
>>-Command window
>>on key label 'F2' set step on
>>do myForm
>>
>>-Go to editbox, ins off, start typing, [F2] when near the end of line
>>
>>Might work.
>>Cetin
>
>I just figured out what the problem is. The text in the editbox that was originally entered had carriage return. That is, user types one line, presses Enter, then next line. In those cases, when you try to type over the exiting text, the line gets pushed down.

I see. You can't type over an nonprintable character and it persists :)
If you want you can remove them on entry :

this.Value = chrtran(this.Value, chr(13)+chr(10), '')

Cetin