Why does this happen?  How to fix it?

Once in a while I get error in ~/ScriptResource.axd?d=...

System.Reflection.TargetInvocationException: Exception has been thrown by
the target of an invocation. --->
System.Security.Cryptography.CryptographicException: Padding is invalid and
cannot be removed.

   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)

   --- End of inner exception stack trace ---

   at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[]
arguments, SignatureStruct& sig, MethodAttributes methodAttributes,
RuntimeTypeHandle typeOwner)

   at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[]
arguments, Signature sig, MethodAttributes methodAttributes,
RuntimeTypeHandle typeOwner)

   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags
invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean
skipVisibilityChecks)

   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags
invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)

   at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)

   at System.Web.Handlers.ScriptResourceHandler.DecryptString(String s)

   at
System.Web.Handlers.ScriptResourceHandler.DecryptParameter(NameValueCollection
queryString)

   at System.Web.Handlers.ScriptResourceHandler.ProcessRequest(HttpContext
context)

   at
System.Web.Handlers.ScriptResourceHandler.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)