I've got a chipped Xbox with Evo-X and recently bought this YUV-Cable:
I switched to NTSC video output with the Enigmah tool and activated the HD possibilities in the original M$ dashboard.
Most games work very good and except for LOTR Return of the King (PAL) every game starts. But while playing some games I get a black screen for about half a second every 10 minutes. Could my Samsung LCD TV be the problem?