Event ID: 1309

Since few days ago we're having a bizarre error. In an ASPX page
(ASP.NET 2.0 - C#) we have a JavaScript error:
"'WebForm_PostBackOptions' is undefined". Researching, we found this
happens only if the applicacion is reached by the public URL (WAN). If
we try to reach the app through the internal URL (LAN), the error
doesn't take place.

Trying to reach the root of the problem, we saw that the web server
throws a warning (Event ID: 1309 - Padding is invalid and cannot be
removed. {This could be related with WebResource.axd file}) when the
page is loaded, and a postback is forced, the JavaScript error take
place.

THIS DOESN'T ENDS THERE. Still trying to reach the source, we found
that the Event Viewer of the ISA Server 2004 (SP4), every time that
the Web Server throws the warning, the ISA Server throws another
warning (Event ID: 23002 - Isa Server was unable to process a response
body from [url] because the response was compressed by teh x-compress
method, which is not supported by ISA Server.).

Thie JavaScript error isn't a simple little mistake, it seems to
generate a lost of session variables. The unique clue we have is that
it could be related with web.config tag machineKey. We change this tag
in all the possible ways and it still fails.

Last item: the applicacion takes a cookie generated by an ASP.NET 1.1
application (with whom shares the same machineKey data).

That's it, no more, no less. =BFAnyone can help us?

THANKS IN ADVANCE!!