>We have a web farm that uses Network load balancing. We have started developing web apps using Visual Studio 2005 and ASP.Net.
>
>We have a problem when any of our .aspx pages performs a postback, sometimes the page works and sometimes the page returns:
> Server Error in /
> Validation of viewstate MAC failed
>
>How can I resolve this error?
>
>Thanks,
>
>Jerry

Jerry,

I haven't had the pleasure of working with a Web Farm so I've never seen that message before. However, knowing how ASP.NET likes things, you may have to mask the MAC address with the farm software, or there may be a configuration in VS 2005 that can manually spoof the MAC address.

I'm guessing that .NET encodes the viewstate using some portion of the MAC address as a seed, which is why it is sensitive to different MAC addresses on sequential post backs.