NON-ECC is fine in an ECC board, but it's very weird that ECC ram works.
Are you sure it's ECC ram?? Has it got the extra controller chip?
the AV8 is a amd64 board, socket 7xx iirc. well all athlon 64 imc's have ecc compatibility, and im pretty sure most boards ive used listed ecc ram as compatible - heck my old KD7 has a bios option to enable/disable it and thats a via Kt400 based socket A board.