Same as browner1980, I don’t have the solution, but have you tried editing your config file and changing the CONFIG_HDMI_BOOST setting? This increases the HDMI signal strength – default is 0, max is 7. The raspberrypi.org site recommends trying a value of 4 if you’re having signal issues.
There’s definitely something funny with the Pi’s HDMI. If I hook it up directly to my receiver (an Onkyo) it doesn’t work properly; I get signal drops every 30 seconds or so. However, routing it through a powered HDMI splitter first results in it working perfectly.