@Cameron ,, Take a look at this thread, http://communities.intel.com/message/172505#172505 .
More and more evidence is pointing to cables, especially low cost varieties, causing the issue on HDMI. The reason you see POST screens is that not all HDMI pins are active during POST and also POST is low resolution, low bandwidth. Once Windows boots you are now at a high bandwidth connection that poorly designed cables may not be able to handle.
I highly recommend purchasing a high quality cable with no adapters such as the one recommended here.