I have had no problems. iTunes sees the 32mb in the 600 and the 64mb in the backpack as one contiguous block of 96 megabytes. Rio/Sonicblue are constantly upgrading the firmware on the players (and there must be a reason). Make sure you have the latest firmware (I updated mine through iTunes). You'll need a particular revision in order for the Rio 600 to see the new back at all.