i assume u can still access that drive (?)...
some ideas just off my head...
Backup most important data 1st. use RAR/ZIP to compress yr files in that drive in manageable chunks and move them to yr computer side. unzip/unrar will naturally check for errors.
As of now, no idea of the source of the problem.
qs
* hdd still accessible?
* how often does that happen so far?
* try different connection cable (USB?)?
* how did u know it's a CRC issue? win popup warning? driver warning? smart warning?
* how old is the external drive?