Tested this again with a 650N with the 2.40 firmware, no issues.
For those that have the BaseCamp transfer fail, please attach the GarminDevice.xml file and the GPX file that BaseCamp writes the waypoints to. It should be in the Garmin\gpx folder on the device, probably the one with the newest time-stamp.
If this is indeed a BaseCamp issue, we will do our very best to fix it, but it's hard to fix something we cannot reproduce.
Perhaps you could explain your problem in a bit more detail? What have you done? What isn't working as expected? Which Garmin 600t do you have?