Hello all,

I made a webform application with ajax. You have to log in and when authenticated you can navigate to a page which contains a dropdownlist. When you select something in this dropdownlist, it executes an ajax callback to the code-behind. (It shows a turning GIF-file and does the needed methods.) It works fine, no errors.
When I connect with remote desktop to a computer and I browse to this site, all works fine.

Now comes the tricky part:
When I connect with remote desktop to a terminal server and try to browse to this site, the server can find the site, I can do a 'login', but when I select something from this
dropdownlist, it throws immediately a Sys.WebForms.PageRequestManagerTimeoutException.

I know you can set the timeout of an asynchronous callback in de scriptmanager tag, but it contains already "36000".

I already googled, but I didn't encounter a problem like this one. (because the terminal server makes it somewhat different) 

If someone can help me with this problem, I would be very gratefull!

Kind regards!

Marc Meers 

Hi, MarcMeers

The problem can happen when the machineKey used to encrypt/decrypt the viewstate was changed, and more likely this will happen if you keep the page idle for a long time or the server cost a long time to hander a request. To avoid this, you need to have a static machineKey.

Check this article http://blog.g9th.com/2007/01/14/unable-to-validate-data-at-systemwebconfigurationmachinekeysectiongetdecodeddata.aspx

Let me know if you need more info.
You can also see this thread for more help: http://forums.asp.net/t/1115331.aspx http://forums.asp.net/t/1114130.aspx

Hope this helps.

Hello Jin-Yu Yin,

 Thank you for the effort you have made.

But, we have found the problem.
Someone changed the MTU value to a lower value than normally used.

We changed it back to the default values, all worked fine after it....

 Thanks!

Case closed...