{ApplicationName} /ScriptResource.axd and Invalid View State

I have an asp.net web form application running in a web farm?

All machine keys are configured the same in web.config as recommended by MSDN, but it occasionally throws "System.Web.HttpException: Invalid view state" and according to the stack.

In this line

Request: / {applicationname} /ScriptResource.axd +92

Note. {filename} is my application name.