val() does not retrieve correct value of the check box checked attribute. See how referring to the element itself returns "true" yet val() return "".

?$row.find("[id$='_cb']:checked").val()

""

?$row.find("[id$='_cb']:checked")[0].checked

true

?$row.find("[id$='_cb']:checked")[0]

{object}

accept: ""

accessKey: ""

align: ""

all: {Count = 0}

alt: ""

attributes: {Count = 108}

behaviorUrns: {...}

border: ""

canHaveChildren: false

canHaveHTML: false

checked: true

childNodes: {Count = 0}

children: {Count = 0}

className: ""

clientHeight: 20

clientLeft: 0

clientTop: 0

clientWidth: 20

complete: false

contentEditable: "inherit"

currentStyle: {...}

dataFld: ""

dataFormatAs: ""

dataSrc: ""

defaultChecked: true

defaultValue: ""

dir: ""

disabled: false

document: {object}

dynsrc: ""

filters: {...}

firstChild: null

form: {Count = 18}

height: 72286252

hideFocus: false

hspace: 0

id: "ctlGrid_ctl04_cb"

indeterminate: false

innerHTML: ""

innerText: ""

isContentEditable: false

isDisabled: false

isMultiLine: false

isTextEdit: false

lang: ""

language: ""

lastChild: null

loop: 1

lowsrc: ""

maxLength: 2147483647

name: "ctlGrid$ctl04$cb"

nextSibling: {object}

nodeName: "INPUT"

nodeType: 1

nodeValue: null

offsetHeight: 20

offsetLeft: 223

offsetParent: {object}

offsetTop: 4

offsetWidth: 20

outerHTML: "<INPUT id=ctlGrid_ctl04_cb type=checkbox CHECKED value="" name=ctlGrid$ctl04$cb>"

outerText: ""

ownerDocument: {object}

parentElement: {object}

parentNode: {object}

parentTextEdit: {object}

previousSibling: { }

readOnly: false

readyState: "complete"

recordNumber: null

runtimeStyle: {object}

scopeName: "HTML"

scrollHeight: 20

scrollLeft: 0

scrollTop: 0

scrollWidth: 20

size: 20

sourceIndex: 50

src: ""

Start: "fileopen"

status: true

style: {object}

tabIndex: 0

tagName: "INPUT"

tagUrn: ""

title: ""

type: "checkbox"

uniqueID: "ms__id1"

uniqueNumber: 1

useMap: ""

value: ""

vrml: ""

vspace: 0

width: 0