I haven't spotted an email from you, so try the following:

If you have any software that uses the serial port installed - Palm sync is the usual culprit - disable it first.

Sorry, I have to ask this - as it is a fairly common mistake. You are connecting over serial and not USB?

The player may have a fault (albeit rare on the Rio-branded units) where it always thinks it is on car power. Go to the settings menu - if you see an option for 'dimmer' (which should only be visible when in the car) then your player needs to come in for service.

And lastly, are you applying power to the player when the upgrade wizard tells you to? The player can only accept an upgrade if it is interrupted in the first second or two of the boot process. If the upgrader doesn't detect the player after a couple of seconds, unplug the power and try again - there is no need to start the upgrader again unless it times out.

You don't have to uninstall the old software first and this won't be affecting the upgrade.