HDMI handshake issue.

Here are some steps you can try.  Hopefully this will solve the issue.  I've had this problem myself with my xbox and my Wii but was able to correct then with the following steps

Situation

If you experience sudden unexpected complete, (not partial), loss of audio & video, video only or audio only the cause may be an HDMI hand shake problem.

Possible causation

With the advent of super fast powering up media (source) devices such as a cable box or satellite receiver data can arrive at an AVR and or HDTV too fast. Think of it this way. You have a garden hose with an attached nozzle. When the water is turned on before triggering the nozzle the water in the hose is backed up. Once the nozzle is opened the backed up water rushes out at an above normal force. This is what happens when a source device using an HDMI cable powers up before the AVR and or TV. The data backs up in the HDMI cable. Once the AVR and or TV are completely powered up the oncoming rush of data may cause a disruption, i.e. HDMI hand shake issue.

Correcting a hand shake problem

Disconnect the source devices HDMI cable from the AVR and from the AVR to the HDTV. If the HDMI cable is routed from the source device directly to the HDTV disconnect the HDMI cable from the HDTV. Wait 10 to 20 minutes then reconnect the HDMI cables. IMPORTANT! Power up the AVR and HDTV completely before the source device. In most instances this should resolve the hand shake issue.

Preventing a hand shake issue from re-occurring

To prevent future hand shake issues ensure the AVR is fully powered up before the source device (sat recvr, cable box, etc.). If the HDMI cable is routed directly from the source device to the HDTV ensure the HDTV is fully powered up.

Better yet power up your AV devices in the following sequence - HDTV, AVR then cable box or satellite receiver. This process is very simple if powering up manually. When using a remote you can achieve the same result by programing in power up time delay for the source device.

You may need to consult the maker of your AVR, HDTV, source device and remote control for brand specific information.

Read more: www.hometheatershack.com/.../46930-correcting-preventing-hdmi-hand-shake-problems.html

Thanks for the answer, but I've already done this.  I'm no stranger to HDMI issues, I work with HDMI stuff at my job.  HDMI over Cat6E and Coax and other baluns.  You know, the fun stuff.  I'll give it another shot, but my 360 is plugged directly into my TV.  It used to work no problem.  Now it's just the HDMI out that doesn't work on my 360, the component works fine.  My laptop sends out a HDMI signal using the same cable and on the same input on the TV.  It's the fact that when my 360 is on and connected to the TV through HDMI, my TV detects a signal of some kind, as I am able to select the input (my TV does not allow you to select an input port that does not have a signal inbound), but there is no audio or video at all.  This leads me to believe that there is an HDMI handshake issue or the HDMI port is going out all together.

Hey Gamer3 8! Thanks for the detail in your post! It sounds like it may be a faulty HDMI port, but just to be sure - are you able to try your console with a new TV? If it doesn't work, then it would be time for a repair. You'd be able to get the ball rolling on that by going here: http://support.xbox.com/xbox-360/repair/repair-process Either way, we'd love to hear what the result was!