jQuery Grid Plugin - jqGrid

I seem to be getting the following error in IE8:

I've tried including the src files and have traced the error to the following line: grid.base.js line 2105

$t.grid.headers[i].el.style.width=cw+"px";

It is affecting the resizing of columns when I switch focus to and from a grid. (I have the grid loaded in a jQueryUI tab, and when I switch to another tab, then back, the columns are the wrong size in IE only.)

It works properly in FF 3.6 and Chrome 4 and 5

any thoughts?

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.3)
Timestamp: Sun, 14 Mar 2010 22:36:43 UTC

Message: Invalid argument.
Line: 108
Char: 416
Code: 0
URI: http://aqs.sitcorporation.com/assets/jquery/plugins/jqgrid-3.6.4/js/jquery.jqGrid.min.js