root cause of "Validation of viewstate MAC failed" in a web farm

Question

We have our application set up in a web farm. Sometimes, on submit of the page, we get the above error; other times the submit happens to be successful, and the postback happens. I seem to suspect one of the machines in the farm is defective. We never faced such a problem on the test box however. So what could be the problem? How do I resolve this? Must there be some setting in the machine.config that should be the same on all machines?

Answer 1

Have you set up MachineKey properly?