Everyday my site gets this error (see below), what is causing this and how can I fix this?

Event Type: Warning
Event Source: ASP.NET 2.0.50727.0
Event Category: Web Event
Event ID: 1309

Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 4/25/2008 12:44:30 AM
Event time (UTC): 4/25/2008 7:44:30 AM
Event ID: 81dfe829e825470a88a66904cffdb06f
Event sequence: 3
Event occurrence: 2
Event detail code: 0

Application information:
Application domain: /LM/w3svc/695076295/root-1-128535821680625000
Trust level: Full
Application Virtual Path: /
Application Path: C:\*********\wwwroot\
Machine name: **********

Process information:
Process ID: 4168
Process name: w3wp.exe
Account name: ********************

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

Request information:
Request URL: https://****************:443/WebResource.axd?d=6VWBbYkUQ5Lg23jJVGplCA2&t...
Request path: /WebResource.axd
User host address: 66.249.65.135
User:
Is authenticated: False
Authentication Type:
Thread account name: ***************

Thread information:
Thread ID: 10
Thread account name: ******************
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, Boolean useValidationSymAlgo)
at System.Web.UI.Page.DecryptString(String s)
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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