Extended Grid - Line border around frozen columns

In the extended grid, when I freeze a few columns I am trying to add a line border around the grid columns using the style definition mentioned below. This works perfectly. The problem is when I remove the frozen columns, I am left with the line border on the first row selector column. How can I completely remove the line border?

.aw-gpanel-left {
border-left: 2px solid black !important;
border-right: 2px solid black !important;
}
.aw-gpanel-top .aw-gpanel-left {
border-top: 2px solid black !important;
}
.aw-gpanel-middle .aw-gpanel-left .aw-frozen-true {
border-bottom: 2px solid black !important;
}

Forgot to mention this. When I unfreeze the columns, I am invoking the following functions. Do I need to call any other functions to clear this?

grid.setFixedLeft(0);
grid.clearScrollModel();
grid.refresh();