Does manually setting the enableViewStateMac property of the asp.net pages to 'true' have any effect? I read that someone actually fixed it by setting it to 'false' which makes no sense to me. that should be the default. I saw this before and it also may occur when users leave a page open for too long and later generate a post back. The maching key is automatically generated and changes prior to the user causing the postback. If you set a static machine key it may help.

This is in C# (there should be a vb example):

http://support.microsoft.com/default.aspx?scid=kb;en-us;Q312906

Not sure it will work in your case, but I guess it's worth a shot unless you find out otherwise.


>Occasionnally, I get this message from an .ASPX page:
>
>"Unable to validate data"
>
>This is the stack trace:
>
>

>at System.Web.Configuration.MachineKeySection.GetDecodedData(Byte[] buf, Byte[] modifier, Int32 start, Int32 length, Int32& dataLength)
>   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
>

>
>This is an error which seems to happen at the .NET level as I cannot trap it in my application. Anyone would know what could be related to that?