Суть в том, что возвращаемая вами структура данных JSON неверна.
Одним из преимуществ jqGrid является использование серверной библиотеки, которая автоматически взаимодействует с клиентской jqGrid.Если по какой-то причине вы обнаружите, что использование этих предварительно собранных серверных библиотек невозможно, то вам нужно сгенерировать JSON в структуре, которую ожидает jqGrid.
Из примера данных JSON jqGrid (http://www.trirand.com/blog/jqgrid/jqgrid.html) ваш JSON должен выглядетькак это:
{"page":"1",
"total":2,
"records":"13",
"rows":[{"id":"13","cell":["13","2007-10-06","Client 3","1000.00","0.00","1000.00",null]},
{"id":"12","cell":["12","2007-10-06","Client 2","700.00","140.00","840.00",null]},
{"id":"11","cell":["11","2007-10-06","Client 1","600.00","120.00","720.00",null]},
{"id":"10","cell":["10","2007-10-06","Client 2","100.00","20.00","120.00",null]},
{"id":"9","cell":["9","2007-10-06","Client 1","200.00","40.00","240.00",null]},
{"id":"8","cell":["8","2007-10-06","Client 3","200.00","0.00","200.00",null]},
{"id":"7","cell":["7","2007-10-05","Client 2","120.00","12.00","134.00",null]},
{"id":"6","cell":["6","2007-10-05","Client 1","50.00","10.00","60.00",""]},
{"id":"5","cell":["5","2007-10-05","Client 3","100.00","0.00","100.00","no tax at all"]},
{"id":"4","cell":["4","2007-10-04","Client 3","150.00","0.00","150.00","no tax"]}],
"userdata":{"amount":3220,"tax":342,"total":3564,"name":"Totals:"}}
Так для вашего набора данных:
{"page":"1",
"total:2,
"records":"1",
"rows":[{"id":"43", "cell":["Test Video","This is a test","Wed Feb 16 00:00:00 UTC 2011",""]}]}