It seems that 5.6.1 update is buggy.

Apart from the error i posted in at first, checking the events i see also tones of a second error. And i'm using a special DNN hosting plan at 3essentials so this is not a hosting problem.


AssemblyVersion: -1
PortalID: -1
PortalName:
UserID: -1
UserName:
ActiveTabID: -1
ActiveTabName:
RawURL:
AbsoluteURL:
AbsoluteURLReferrer:
UserAgent:
DefaultDataProvider:
ExceptionGUID:
InnerException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
FileName:
FileLineNumber: -1
FileColumnNumber: -1
Method:
StackTrace:
Message: DotNetNuke.Services.Exceptions.PageLoadException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. ---> System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. ---> System.Web.UI.ViewStateException: Invalid viewstate. Client IP: 46.109.202.61 Port: 51871 User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; FREE; .NET CLR 1.1.4322) ViewState: 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... --- End of inner exception stack trace --- at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidati ) at System.Web.UI.ViewStateException.ThrowMacValidati (Exception inner, String persistedState) at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString) at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState) at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState) at System.Web.UI.HiddenFieldPageStatePersister.Load() at System.Web.UI.Page.LoadPageStateFromPersistenceMedium() at System.Web.UI.Page.LoadAllState() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace ---

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Discover Venice

I had this same error, and at the bottom of the screen the dontnetnuke logo appeared together with the error message. I Remarkd that (1) the error seemed only to be present under Firefox and not under IE, and (2) the error referred to a missing object for compression. So i set the compression option under Host> host settings > performance settings to No Compression (I had to redo this several times, seemingly teh system first refursed to do so), cleared the cache, set the cache option to No Cache, and seemingly the error disappeared.
Sorry that I cannot give more detail, but this is on a production site, and I cannot reproduce the error just to see what is going on. If needed, mail me at herman.claus@nck-cnc.be .
I also have the idea that the error was not present at the beginning, after updating tot 5.6.1., but only started to manifest itself this weekend, but I am not sure about it.