I am transactionally replicating SQL 2005 64-bit to both 2005 32-bit and 2000 32-bit without any problems.
1. Verify both publisher and subscriber as setup as linked servers.
2. Verify all SQL services (MSSQL, MSSQL Agent, Distributed Transaction Coordinator) are using an account with administrator network access to both servers.
3. If you have not done so already, see Microsoft article "You may receive an error message when you try to run distributed queries from a 64-bit SQL Server 2005 client to a linked 32-bit SQL Server 2000 server" at http://support.microsoft.com/default.aspx?scid=kb;en-us;906954