An asp.net web application deployed to a remote server is returning a hundred of these errors per hour. They began when I upgraded the environment from .net 4.0 to .net 4.5. I tried further upgrading to .net 4.5.1 and even brought it back to .net 4.0 but I cannot stop these errors occurring. The web.config has MachineKey.DecryptionKey specified, though I don't know where I got the value for the key. All the errors refer to WebResource.axd. With the orginal upgrade, I made some changes to an asp:Menu. The only NuGet package being used is AjaxControlToolkit, which I need to keep synchronised with changes to the .net version. I'm at a total loss of what to do, and it's urgent.
Stack trace: at System.Web.Configuration.MachineKeySection.EncryptOrDecryptData(Boolean fEncrypt, Byte[] buf, Byte[] modifier, Int32 start, Int32 length, Boolean useValidationSymAlgo, Boolean useLegacyMode, IVType ivType, Boolean signData)
at System.Web.UI.Page.DecryptString(String s, Purpose purpose)
at System.Web.Handlers.AssemblyResourceLoader.System.Web.IHttpHandler.ProcessRequest(HttpContext context)
Robert