I've had almost the identical same proble when using a hookup to a TV monitor. If everything is OK during the boot it progresses nicely. But if any hardware gets changed etc. the computer tries to send a message during the boot but it doesn't end up on a visible screen even though it is awaiting a user keystroke like F1 before finishing the boot.
Unhook it from the TV and use only the single computer monitor and now see if it boots all the way.