Yesterday I exported 6 routes from BaseCamp to an SD card that I use in a Zumo XT. One of those routes would not import on the XT. I thought it was due to a corrupted export but I discovered that I could not delete or overwrite the associated .gpx file on the SD card. I eventually solved the problem by using the Windows chkdsk command to fix a file integrity issue on the card. So, this is an FYI advising that if you have a problem with files written to an SD card, check its file integrity.