Viewstate Invalid -- Please Help!

[Paul]

Background:
I wrote an ASP.NET website in C# and it went into production back in
February 2004. The production webservers (2 servers using sticky-ip
load balancing) are running on Windows 2000 server. I have changed
the machineKeys to match on both servers since they are pseudo-Load
Balanced. The website is using Forms Authentication and the userid &
password are stored in a SQL Server 2000 Database. There are not any
dynamic control creation sections on the page.

Problem:
These HttpExceptions are happening periodically on every page
including the login page. I have turned off the enableViewstateMAC in
the machine.config file and we no longer had any HttpExceptions. Due
to the security risk I have turned that feature back on and am trying
to find a solution to this issue. As soon as I changed the
"enableViewstateMAC" from false to true we recieved several errors.
All the errors that have happened so far are only on the login page so
it is before the user even logs in.

You can view another discussion that I have had on the Code Project
website http://www.codeproject.com/script/comments/forums.asp?msg=785002&forumid=12076"]
if you would like to find out more background information about this
problem.

Thanks for your help,
Paul