Use SQL2005 To Decrypt EncryptedData XML Created In .Net

http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=384472&SiteID=1
I suppose that some of the answer to my question may be found in that topic, but I haven't made much progress.
I have a text field in a SQL 2000 database that contains the text output (EncryptedData) from the EncryptedXML.Encrypt(xmlDoc.DocumentElement, certificate) method in .Net 2.0 (C#). The data looks something like this:

<?xml version="1.0" encoding="utf-8"?>

<EncryptedData Type="http://www.w3.org/2001/04/xmlenc#Element" xmlns="http://www.w3.org/2001/04/xmlenc#">

<EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes256-cbc" />

<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">

<EncryptedKey xmlns="http://www.w3.org/2001/04/xmlenc#">

<EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-1_5" />

<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">

<X509Data>

<X509Certificate>[A Bunch of jumbled characters]</X509Certificate>

</X509Data>

</KeyInfo>

<CipherData>

<CipherValue>[A Bunch of jumbled characters]</CipherValue>

</CipherData>

</EncryptedKey>

</KeyInfo>

<CipherData>

<CipherValue>[A Bunch of jumbled characters]</CipherValue>

</CipherData>

</EncryptedData>

I have since imported the Public and Private key from the .Net app into SQL Server. I can use the EncryptByCert and DecryptByCert functions to verify that the key pair is compatible. However, I can't figure out how to apply them to the encryptedXML that my friendly .Net developers are dumping in the DB. Whenever I use the DecryptByCert function on any of the "[A Bunch of jumbled characters]" strings I just get NULL.
Does anybody have some insight?