Hi Bob,
It would be great if you can answer these questions for a better understanding of this issue.
1) Are you able to copy large amount of files to the same SD Card from any other locations (like the Library Folders) on the computer?
2) Did you try using another SD card and check the issue?
3) Did you enable the option “Access all files offline” in the SkyDrive app PC Settings?
If you have enabled the option “Access all files offline” in the SkyDrive app PC Settings, then the issue could be due to this. You may turn OFF this option on the computer.
If the issue happens only with the SkyDrive and you are able to copy large amount of files from all the other location on the computer, then this could be an issue with the SkyDrive. Please get back to us with the additional information for further assistance on this issue.