Hello,
I have a problem with the File Manager and File Upload in DNN 3.3.7.
I saw several Posts about this, but these solutions doesn't help me, or I did not find the right one.

The problems:

• By Synchronize Files or Upload Files (in Admin and Host File Manager) the follow crittical error shows:
  Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.
• When I want to use File Upload, for example to add/update Modules, no error comes. (Also not in the error log). So I cannot update my Modules.

When I use the Image Module, and upload a picture with this Module, I have no problems.

The Error log says:

AssemblyVersion: 03.03.07
PortalID: 0
PortalName: VZC Veenendaal
UserID: 1
UserName: host
ActiveTabID: 46
ActiveTabName: File Manager
RawURL: /Admin/FileManager/tabid/46/Default.aspx
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer: http://vzcveenendaal.04.websecurestores.com/Admin/FileManager/tabid/46/Default.aspx
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.4) Gecko/20070515 Firefox/2.0.0.4
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: bd74ff7d-a8b2-4e02-9f02-694ded00d282
InnerException: Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: System.Web.UI.ClientScriptManager.ValidateEvent
StackTrace:
Message: DotNetNuke.Services.Exceptions.PageLoadException: Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation. ---> System.ArgumentException: Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation. at System.Web.UI.ClientScriptManager.ValidateEvent(String uniqueId, String argument) at System.Web.UI.Control.ValidateEvent(String uniqueID, String eventArgument) at System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace ---

Who can helps me?
BTW, I tried already to change the Validation, in the web.config ,  in true and false.

My provider support ASP2.0, but I have not enough DNN-knowlegde (yet) to be sure the update to version 4 will by safe.

The last rows of the system.web-part in web.config are (Or do I change the wrong part?):

<!-- page level options -->
<pages validateRequest="false" enableViewStateMac="true" />

I tried: both both true, both false and false/true and tru/false.

Thanks in advance,

Corné