I recently added a delegate control to a SharePoint solution. The delegate control was used to dynamically insert a custom user control into the master page. Part of the functionality of this control required the use of hidden fields.
Everything worked perfectly until I tried to add or update a workflow against a list. After clicking Next on the add workflow page, the following error was thrown:
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that