I have 2 problems related to my XBox 360 not working properly with my 57LX177 when connected via HDMI:

1) Months ago I had my 360 hooked up to my Toshiba 57LX177 with HDMI & no problems but because I had to do renovations I packed up & stored my Toshiba & gamed on my older Samsung DLP set.
I just unpacked the Toshiba & hooked it up with HDMI but I get NO audio/video. The TV screen displays that it is not receiving a signal.
I checked the HDMI cable by connecting it to my cable box & it worked fine so its not the HDMI cable or the ports on the TV (when I connected my 360 to the Toshiba via RGB I had the same problem, no picture) the only way I can get a picture is with the Component cables.

2) My 360 controller will not sync up with my console when the console is connected to the TV via HDMI, but it works fine when I use a component cable.

Any help anyone can offer would be greatly appreciated.

Your controller not being able to sync up should have nothing to do with what cable is used to transmit video/audio to your display.

As for the cable issue, it sounds as if the settings are jacked in the 360 system menu. Try hooking it up via component and setting everything to the default settings and then try using the HDMI cable.

Just to check: Are you selecting the correct input on your display when hooking it up via HDMI?