var xmlResult:XML = XML(event.result);

trace(xmlResult.toXMLString());  //So you know how to write the xmllist expression

var xlJobs:XMLList = xmlResult.job;

trace(xlJobs.length());  //is this number what you expect?

datagrid.dataProvider = xlJobs;

http://tech.groups.yahoo.com/group/flexcoders/message/113539

Tracy from FlexCoders advises against using lastResult.  This property is intended for use in binding expressions, and you cannot depend on its value when you access it in AS code (though it usually works).  

Note that if you ever decide to use binding instead of directly assigning the dataProvider, do not use XMLList because it is not bindable.  Wrapt that in an XMLListCollection instead.

Flex XMLListCollection

xml

ActionScript