Sync on green has nothing to do with the x2vga transcoder. Sync on green has only to do with a monitor in conjunction with the vga bios and a modded cable. Having a SOG monitor voids the need to add a sync seperator when using the vga bios.
Also, there is no xvga1, or x1vga. It has always been x2vga; they just made it more compatible with the newer versions of the xbox with the focus chip.
The x2vga is very compatible with most any monitor. Most likely your problem is that you don't have the right dip switch setting for the monitor your using. The x2vga comes in default H&V sync dip setting. If that doesn't work, try the other setting, composite: First down, two and three up, and the forth down.
Ok. I thought you used a X2VGA...
g-sas: Maybe it's just me, but that device looks like crap...
Ok, you have the digital-x transcoder; the german made vga adapter. They were one of the first to make a true vga adapter for the xbox. I remember when they first came out. The digital-x adapter only supports 480p. While the compatability isn't high, and there is some too dark issues with the adapter, it is a good transcoder. My advice is to upgrade to an x2vga. It gives a much better, brighter, vibrant picture, and much more compatible with a wide variety of monitors than the digital-x transcoder.