I got this error if there is no activity on the application after 40/60 second, my live server is not hosted by a web farm or cluster
I've seen lot of posts about this, with some solutions by adding new key in the web config but nothing is working for me
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
Any ideas are welcome
Franck Merlin
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