I have an LG G2 and Windows 7 operating system, I've been having this problem on Linux too. Basically Any command I issue to the phone with fastboot gets stuck at some point. If I try to flash recovery fastboot hangs at
fastboot devices returns a question mark.
I have usb driver installed, Adb sees phone during normal operation (I'm on on Windows-7), fastboot doesn't see it when in fastboot mode. If I try to use Android SDK latest usb drivers Windows 7 says it has already the latest drivers for my phone.
This is what happens when I send
fastboot flash recovery recovery.img
target reported max download size of 1862270976 bytes sending 'recovery' (11056 KB)... OKAY [ 0.406s] writing 'recovery'...
And then the process hangs there. There was a time when doing the same operation yielded the error message "too many links" or something similar I cannot remember exactly or reproduce it again.