MouseOver row highlight - Moves row text up and down

Hi,
I've noticed that a couple of other ppl have posted about this behaviour.

I'm trying to achieve a similar affect to A:hover when I mouse over a row in the grid. (i.e. a line under the row currently being hovered over)
My style is as follows:

.aw-mouseover-row {
border-bottom: 1px solid rgb(153,0,0);
cursor: pointer;
}

I've noticed that when I mouse in to the row the row text moves up a pixel. When I move the mouse back out the row text moves back down to its original position.

Does anyone know why this is happening or if it can be fixed?

Thanks in advance for any help on this.
BT