Oh, when the unit is powered, the only thing on its display is the large Rio logo. None of the buttons do anything at all. I have no idea if this is normal/expected behaviour when used for the first time and no music has been synced.

This is not normal behavior, and it is the reason for all your problems.

The unit most likely has a loose disk drive cable. You may contact support for under-warranty-sanctioned help in diagnosing the problem.

If you don't care about the warranty thing, you're welcome to open the player and look for a loose cable yourself. Look in the FAQ regarding disk drive upgrades for complete disassembly instructions.