An error occurred while encrypting a control's callback state

Error Description:

This error occurs if you host a web application in a web farm and encryption keys for this application are generated at runtime.

Solution:

To solve this issue, assign a key value to the machineKey element’s decryptionKey attribute in the configuration file:

xml

<machineKey 
    validationKey="your-validation-key" 
    decryptionKey="your-decryption-key" 
/>