Jquery 1.4.2 Form submit event handler is firing after form submit in IE 7/8

Jquery 1.4.2 Form submit event handler is firing after form submit in IE 7/8

I am facing issue in form submit event handler. here is my code I am using Jquery 1.4.2
 
<FORM id = "mysearchform" method = "get" action = "http://www.abc.com/results.aspx?q=" target = _blank sizcache = "1694" sizset = "0" jQuery1347023310528 = "3" > <DIV class = "search" > <span><span> <LABEL class = hide for = q > Search: </LABEL> <INPUT accessKey = S id = "a" class = "abc" name = "a" maxLength = "50" value = "Images" size = 69 type = "search" autocomplete = "off" selectionStart = "0" jQuery1347023310528 = "108" > <INPUT style = " WIDTH : 185px ; HEIGHT : 33px " class = "img" title = "Search" alt = "Search" value = "Search" src = "http://dummyimage.com/180x35" type = image > <INPUT name = "form" value = "abcd" type = "hidden" ></SPAN></SPAN></DIV> </FORM>
 

I have one event handler for mysearchform which is used to change value of form input element and value of text box with id "a" so that on form submit I can change value of text box i.e. (add additional value)

$("#mysearchform").submit(mysubmitHandler);

in mysubmitHandler, I am changing values for "a" and form input element. This code is working fine in IE9, FF 4.0 and latest version of chrome. However in IE 7 and IE8, before coming to "mysubmitHandler", new window is opening (I am showing search result in new window). So my changes in are not getting appended to query string on search window.

in other browsers, "mysubmitHandler" is firing first and then new window is opening so I am getting expected results. Any help?