Error for Windows authentication for NAV 5 and NAV 2009

Good morning for everybody,

A customer got SQL 2005 (mixed mode) running under Windows Server 2003 R2 Standar X64 SP2 . and uses NAV 2009 R2 windows authentication (extended procedures created) and NAV 5.0 SP1 windows authentication under same server.

We can connect to NAV 2009 using Windows authentication but we cannot connect to NAV 5 using Windows authentication and we got same error that appears when extended procedure is not created (both procedures must be created to use windows authentication), but both have been created using 64 bits dlls and is working for NAV 2009.

Do you know if there is a compatibility problem between versions and 64 bits or other problem?

Thanks so much in advance

Juanan