Need Help with XPCOM Exception in getPrintPreviewNumPages

Hi,

I have embedded Gecko engine , successfully loaded and obtained the
Document.But My goal is to get the page count of the loaded document.

getPrintPreviewNumPages() throws exception as shown

Exception in thread "Thread-3" org.mozilla.xpcom.XPCOMException: The
function "printPre
viewNumPages" returned an error condition  (0x80004005)
        at
org.mozilla.xpcom.internal.XPCOMJavaProxy.callXPCOMMethod(Native
Method)
        at
org.mozilla.xpcom.internal.XPCOMJavaProxy.invoke(XPCOMJavaProxy.java:
140)
        at $Proxy11.getPrintPreviewNumPages(Unknown Source)
        at DocumentProcessor.run(DocumentProcessor.java:132)
        at java.lang.Thread.run(Unknown Source)

My code is as shown.What am I missing?

stuck in this for past few days.

I also tried  with proxy object for print but same exception.

nsIWebBrowserPrint printProxy =
(nsIWebBrowserPrint)proxy.getProxyForObject(eventQueue,nsIWebBrowserPrint.NS_IWEBBROWSERPRINT_IID,
renderer.print,nsIProxyObjectManager.INVOKE_SYNC);

regards,
Krith