Direct Encryption and decryption

 I developed an Asp.Net site using VS2005 SP2 in XP SP3. Then publish
it in a Windows 2000 Advance Server SP4 which has DotnetFx2.0
installed. Now when run the site from this server using IE6 SP1 getting
the following error. What I am missing here?
Direct Encryption and decryption using RSA OAEP padding are not available on this platform.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Security.Cryptography.CryptographicException: Direct Encryption and decryption using RSA OAEP padding are not available on this platform.

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