tab focus lost only IE

obj.setController("myTabKeys", {
onKeyTab: "selectNextCell",
onKeyShiftTab: "selectPreviousCell"
});

when tab press, change cell, but focus lost.
click in cell, focus return.

why?! bug?! please anwser me!

obj.onCellTextChanging = function(text, column, row){

if (column == 1) { // column-1 only
if (text.match(/[^0-9.+-]/)){
return "error"; // prevent non-digits
}
}
}

obj.onCellTextChanging + obj.setController("myTabKeys", {..} = bug in IE????????

with grid.refresh, cell focus lost.
not bug, bug is me!

sorry!