I know this subject has been heavily discussed but I haven't found an answer for the problem.
This has nothing to do with having an Android phone plugged in to the USB.
I'm running LR 5.7 64-bit on Windows 8.1
i7 quad core 2.5Ghz with 16Gb DDR3L. LR is installed on my SSD boot drive and LR library sorted in my HDD.
When importing files (RAW, JPEG, TIFF...whatever) via USB 3.0 (flash drive or CF card reader) LR has a tendency to crash my system. It happens a LOT. And ONLY when Importing files into LR - my rig never hangs otherwise.
Have to hard reset and try again.
I haven't yet tried going back to 5.5 as others have suggested, since people are getting mixed results from that work around.
System crashes are either hardware malfunctions or drivers that are not up to date.
One possibility is that your fans are not keeping the CPU cool enough, causing overheating and crash.