If you use iTunes
supportforums.blackberry.co... If you don't.....
- don't use USB3 ports
- Remove all BlackBerry related software (Blend, LINK, Drivers - older desktop software if you have it)
- Reboot
- Disable all malware and virus scanning.
- Redownload and install latest bundled version of Blend (BLEND, LINK, DRIVERS)
- reboot and try again...