I'm using ASP.net 3.5. I keep getting this error message, but I think it is due to it timing out after 15 minutes.
Here is the error message:
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
and this is my webconfig file