I discovered that if I upload from GPSMap 60CSx to BC and export to my PC as gpx I can't upload it to Garmin Connect. This is a well known issue in other Garmin fourms. Workaround is to set the 60CSx to also store tracks on the SD card, then set it to USB after connecting to the PC. Then browse to it with Connect and upload faultlessly. One user reported that the problem is the BaseCamp export does not include time and elevation.
Just thought someone in the BaseCamp development team should know.