Page Method failed after form Submit

See more:

Javascript

.NET

forms

ExtJS

here is My Master page forms:

<form id="form1" runat="server" style="padding: 0; margin: 0; height: 100%;">
----
<div id="XYZ"></div>
---
----
</form>
<form id="form2" method="post" action="">
        <input type="hidden" id="RPTHtml" runat="server" />
        <input type="hidden" id="RPTPara" runat="server" />
        <input type="hidden" id="RPTResult" runat="server" />
    </form>

And
in javascript
----

PageMethods.CreateChart(XYZ.ID, nCountryNo, InStr_nDivisionNo, InStr_PositionNo, iYear, InStr_Month, '', '0', nCustomize_Min, nCustomize_Max, nCustomize_Step, onSucceed, onFailure, Obj_arr); 

(It's running in loop for 10 time (10 other DIV))
---
---
(And other buttom Click event has code something like this)

var srcurl = 'data.aspx?M=getHTMLToPdf'
    form = Ext.get('form2').dom
    form.action = srcurl;
    form.submit();

and if this button is Pressed between loop time of page method then
all remain page method throw "server mathod failed " Error , Even it's Success at Server side.

How to prevent this?