Javascript – using mouseover/mouseout in gridview with alternating rows

I currently have a gridview with alternating colors, Silver and White, with a blue header (not selectable, obviously). Initially, I had this onmouseover/onmouseout thing working but for some reason, yesterday morning it failed to work, and all day yesterday, I have been struggling, googling for answers and coming up short. Here is the databound function:

protected void GridView_OnRowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            e.Row.Attributes.Add("onclick", "onGridViewRowSelected('" + j.ToString() + "')");
            e.Row.Attributes.Add("onmouseover", "HighlightOn(this)");
            e.Row.Attributes.Add("onmouseout", "HighlightOff(this)"); 
        }
    }

And here is the onmouseover and onmouse out functions:

function HighlightOn(rowid)
{   
    if (document.getElementById(gridViewCtlId).disabled == false)
    {
        if ($(selectedIndex).val() != rowid.rowIndex)
        {
            rowid.style.backgroundColor = '#8FBAEF';
        }
    }
}

function HighlightOff(rowid)
{
    if (document.getElementById(gridViewCtlId).disabled == false)
    {   
        if ($(selectedIndex).val() != rowid.rowIndex)
        {
            var modIdx = rowid.rowIndex % 2;
            if (modIdx == 0)
            {
                rowid.style.backgroundColor = 'Silver';
            }
            else
            {
                rowid.style.backgroundColor = 'White';
            }
        }
    }
}

selectedIndex is being set by this:

function getSelectedRow(rowIdx)
{
    getGridViewControl(rowIdx);
    if (gridViewCtl != null)
    {
        $(selectedIndex).val(rowIdx);
        return gridViewCtl.rows[rowIdx];
    }
    return null;
}

This function just gets the row by giving it the id of the row in a gridview (used for the onclick event to change the color of the row).

The problem is this: When I click on a row, it becomes highlighted. When I then move the mouse, the other rows become somewhat highlighted, which is correct, but when I click on another row, and move the mouse out of that row, it becomes de-highlighted. And when i click on it again, does it stay highlighted. selectedIndex is just a hidden field on the page. Does anyone see why this doesn't function properly? Thanks.