david,
In regards to the transfer of the whole playlist, I suggest you take a look at version 8 of MJ. We did a redesign of how we handle file transfers to Portables to accomodate this request. In v8 you can drag and drop files to whatever subfolder you want on your Portable. You can rearrange and delete files as you want and when you are ready click on "Upload" to send all the files in one batch.
In regards to the files not showing after the transfer, are the files actually on the player? My guess is no. If this is true, then you have some incompatible Rio drivers installed. Try removing our Plug-in, disconnecting your Rio, and then follow the instructions at
http://www.riohome.com/support/rio/default.asp?menu=support&submenu=Legacy_Rio&item=faqs&product=Rio_500_PC#20399This will fully remove the Rio drivers you have installed. With the Rio still detached, redownload our Plug-in. Connect your Rio. If your PC tries to find drivers for the Rio, do not allow it to default to its own drivers, point it to the system32 directory (under WINNT if you have 2000 or XP)and let it find the drivers from there.
After this, I think you will be set. Please feel free to email me at steve@jriver.com if you have follow-up questions.