Padding is invaild and cannot be removed

[mjweiner]

I have an ajax.asp.net application that is running very well, however,
my error log is continuing to fill with "padding is invalid and cannot
be removed" These errors report that the url with the error is
http://www.mysitename.com/ScriptResource.axd?d=[different query string
each time]

Here is a sample of what is returned:
Error Message: Padding is invalid and cannot be removed.
error Source: mscorlib
targetSite: DecryptData
Stack Trace:
at
System.Security .Cryptography.R ijndaelManagedT ransform.Decryp tData(Byte[]
inputBuffer, Int32 inputOffset, Int32 inputCount, Byte[]&
outputBuffer, Int32 outputOffset, PaddingMode paddingMode, Boolean
fLast) at
System.Security .Cryptography.R ijndaelManagedT ransform.Transf ormFinalBlock(B yte[]
inputBuffer, Int32 inputOffset, Int32 inputCount) at
System.Security .Cryptography.C ryptoStream.Flu shFinalBlock() at
System.Web.Conf iguration.Machi neKeySection.En cryptOrDecryptD ata(Boolean
fEncrypt, Byte[] buf, Byte[] modifier, Int32 start, Int32 length,
Boolean useValidationSy mAlgo) at
System.Web.UI.P age.DecryptStri ng(String s)
--------------------------------------------------------------------------------
queryString: d:L95-
M7qWbZMBbXmabf5 PWx3fNmkgQWMFBv 1RzXuSwtN2JEE0D fXgC9QntyODxHxw hZ8-
GkJn_QWrfoxAZFj ZGg2
t:6330729738011 59573

I am not running this on a server farm and have changed the <machine
keyin my web.config without effect. Anyone with any thoughts on
what is causing this error?

thanks,

Matt