AbleCommerce Shopping Cart Software

I fond an error in my Event Viewer at my server:
in Application:
Event message: An unhandled exception has occurred.
Event time: 12/19/2008 6:45:36 PM
Event time (UTC): 12/20/2008 12:45:36 AM
Event ID: 5d4c89955510409b9848cc14e409f87c

Process information:
Process ID: 4844
Process name: w3wp.exe
Account name: NT AUTHORITY\NETWORK SERVICE

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

Request information:
Request URL: http://www.mysite.com/ScriptResource.ax ... 3517180357
Request path: /ScriptResource.axd
User host address: 72.44.39.21
User:
Is authenticated: False
Authentication Type:
Thread account name: NT AUTHORITY\NETWORK SERVICE

Thread information:
Thread ID: 9
Thread account name: NT AUTHORITY\NETWORK SERVICE
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)


How Can I fix it?