Short response to the person wanting the ICE from Frankfurt to Paris...
Although ICE trains are almost all no-reservation-required in Germany, I believe when that crosses the French border, a reservation is required. I rode the TGV version of that train about a month ago going the other direction, and you needed a reservation in France, but as soon as it entered Germany, the requirement was lifted.
Additionally, SNCF may be limiting the number of railpass reservations available on the Paris-Frankfurt trains, half of which are French TGV and the other half are German ICE, with mixed crews. Not sure if the limitation is popping up in Deutsche Bahn's computers as they tend not to limit these things.
Best advice, skip RailEurope and make an international phone call to Deutsche Bahn (this is a good opportunity to learn how to use Skype or GoogleVoice). Ask for an english speaker, and tell them you have a railpass and want to make ONLY a seat reservation for that train. Ask them if the number of railpass reservations is capped for that train. If it is, ask how to make a reservation and what the options are for ticket delivery (emailed pdf?).
Good luck.