Padding Warning?

[Smokey Grindel]

Every so often I get this warning event in the event log, what exactly does
it mean and is there any way to prevent it? thanks!

Event Type: Warning
Event Source: ASP.NET 2.0.50727.0
Event Category: Web Event
Event ID: 1309
Date: 1/23/2009
Time: 12:00:01 PM
User: N/A
Computer: WEB
Description:
Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 1/23/2009 12:00:01 PM
Event time (UTC): 1/23/2009 5:00:01 PM
Event ID: 49bc5b1bc0a54e3c82fba4187019b87a
Event sequence: 3
Event occurrence: 1
Event detail code: 0

Application information:
Application domain: /LM/W3SVC/2113717294/Root-1-128772036008178598
Trust level: Full
Application Virtual Path: /
Application Path: C:\Inetpub\wwwroot\********\
Machine name: WEB

Process information:
Process ID: 3728
Process name: w3wp.exe
Account name: R******\R*******Web

Exception information:
Exception type: CryptographicException
Exception message: Padding is invalid and cannot be removed.

Request information:
Request URL:
https://r***.r********.com:443/WebR...YjkrAvqhWPLMXMAOWtuHhvA2&t=633570849513490375
Request path: /WebResource.axd
User host address: 206.180.71.82
User:
Is authenticated: False
Authentication Type:
Thread account name: RE*****\R*****Web

Thread information:
Thread ID: 1
Thread account name: RE******\R******Web
Is impersonating: False
Stack trace: at
System.Security.Cryptography.RijndaelManagedTransform.DecryptData(Byte[]
inputBuffer, Int32 inputOffset, Int32 inputCount, Byte[]& outputBuffer,
Int32 outputOffset, PaddingMode paddingMode, Boolean fLast)
at
System.Security.Cryptography.RijndaelManagedTransform.TransformFinalBlock(Byte[]
inputBuffer, Int32 inputOffset, Int32 inputCount)
at System.Security.Cryptography.CryptoStream.FlushFinalBlock()
at
System.Web.Configuration.MachineKeySection.EncryptOrDecryptData(Boolean
fEncrypt, Byte[] buf, Byte[] modifier, Int32 start, Int32 length, IVType
ivType, Boolean useValidationSymAlgo)
at System.Web.UI.Page.DecryptStringWithIV(String s, IVType ivType)
at
System.Web.Handlers.AssemblyResourceLoader.System.Web.IHttpHandler.ProcessRequest(HttpContext
context)
at
System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&
completedSynchronously)


Custom event details:

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http://go.microsoft.com/fwlink/events.asp.