It seems there was used wrong variable inside setGridWidth method which cause an exception in IE8:

Line: 10
Error: 'grid.cols[…].style' is null or not an object

Fragment of code for grid.base.js is:

setGridWidth : function(nwidth, shrink) {

…

var cle = $t.grid.cols.length >0;
$.each($t.p.colModel, function(i) {

…

$t.p.colModel[lvc].width += cr;
cw= $t.p.colModel[lvc].width;
$t.grid.headers[lvc].width = cw;
$t.grid.headers[lvc].el.style.width=cw+”px”;

if(cl>0) $t.grid.cols[lvc].style.width = cw+”px”;

//instead shoud be used if(cle) $t.grid.cols[lvc].style.width = cw+”px”;

…

}

…

}