hi just recently got a new k70 rgb and had at least 3 of the above problems
my solution was much simpler and safer than messing with bios settings
also tried all the usb 2 n 3 port configs made no difference
go into msconfig and services tab, tick hide all ms services then disable all apply, restart,
then if that solves the problems you probably have a conflict with a unused/forgotten/broken/deleted program, as you collect loads of these over time...
then you can go back into msconfig and enable just the things you use or need regular
like corsair utility, anti virus etc etc one at a time restart between each, until you find the culprit
worked for me... now no freezes crashes (yet lol) and fast boot times
Hope this helps someone