I am getting the following error message when trying to import raw photos into Lightroom CC:
"these files cannot be opened by lightroom"
Is that the exact unedited word-for-word error message? If not, please provide the exact error message.
Try a different memory card, a different card reader (that is if you are using one and if not try one instead of connecting the camera to the computer), a different USB cable (whether or not you are using a card reader or connecting the camera to the computer).
Sounds like the files are getting corrupted during the transfer from card to computer hard drive. Or the actual RAW data is corrupted on the card and LR is initially showing you the embedded JPG at the time of import.
Which camera are you using?
Please provide an example file to verify