jQuery Grid Plugin - jqGrid

Hi,

I am using verision 4.4.5. I have a grid using multiselect and it works fine when I click check/uncheck all button on the header but when i tick the checkboxes individually, it always returns []. Here is my option:

caption: "Devices",

url: ctx + "/device/findForGcm", 

datatype: "json", 

height: 400, 

width: 300, 

colNames:['Device ID','Name'], 

colModel:[ {name:'deviceId',index:'deviceId', width:100}, 

      {name:'displayName',index:'displayName', width:120}

      ], 

rowNum  :10000, 

scroll:1, 

loadonce:true, 

mtype: "GET", 

rownumbers: false, 

pager: '#pager', 

viewrecords: true, 

sortorder: "asc", 

multiselect: true, 

multikey: "ctrlKey",

hidegrid: false

Can you help me what I am missing?

Thanks in advance.