如题，对于jq-grid的colModel属性key有关说明：
http://www.secondpersonplural.ca/jqgriddocs/_2eb0fihps.htm
摘抄如下：
In case if there is no id from server, this can be set as as id for the unique row id. Only one column can have this property. If there are more than one key the grid finds the first one and the second is ignored.
所以当你列表字段制定多个UK时自动忽略，只能制定一个PK。（这点而言怕是根据name取class方便取得才如此设计的）
因此主键字段数据不唯一时会报如题的错。如图。
另外官方的bbs里有哥们nomanirvana也提到过此问题：
http://www.trirand.com/blog/?page_id=393/help/ie7-on-row-click-error-classname-is-null-or-not-an-object-after-upgrade/
解决办法应该就是联合主键联成一个PK作为隐藏key字段。