PageRequestManagerServerErrorException: 404 ??

I have a error when I use Server.Transfer and ASP.NET AJAX.

STEPS:

1- navigate to a page containing a UpdatePanel using SERVER.TRANSFER
2- (first) async call works fine

3 - click again to make second async call and somehow the page path becomes
invalid; the page name is correct but the path seems to belong to the
referer!! (Consequently a 404 server response is returned by the server. see
attached error message )

Anyone help-me?

Server.Transfer really doesn't work well with ASP.NET AJAX. A few people have done some complicated stuff to get it to work, but I recommend just avoiding it altogether if possible. Search around here on the forums, and you can probably find some older discussions of this.