I have simple php application, it works on all browsers except on IE8 beta 2, problem occurs when I try to update table field using Ajax call (jQuery post method). Using IE8
I don't have IE8 myself, but your cookie might be blocked by Internet Explorer's strange security policies. A possible workaround can be to employ P3P (which is also the method for getting cookies working inside an IFRAME).
Generating the right P3P policy can be a bit of work, but you should be able to find the information you need at http://www.p3ptoolbox.org/