If you're running through a new AV receiver, chances are that the issue is with the AV receiver (or how you have it configured) and not with the Xbox 360. Possible issues:
1) There may also be an HDMI input associated with that same input channel on the AV receiver, and you may have to manually configure the AV receiver to tell it "use the component video for this input, not the HDMI". I find this to be a common issue when one "source" has multiple potential inputs, and hence this used to be an issue with a lot of AV receivers when having to select between using analog and digital audio inputs for a given source.
2) If you have the output from the AV receiver connected to your TV via something other than component, e.g. via HDMI, you may have to adjust settings for conversion from component to HDMI.
3) You may need to disable automatic display discovery in the Xbox 360 settings.