Peripherals won't work with Yosemite

I switched to Yosemite in autumn 2014 and it worked. Since I moved house and reassembled my Mac Pro and all its peripherals I've had problems. Both of my Apple USB keyboards now won't work. They each have the same problem - when plugged in they show the cap locks green light but nothing else. My Logitech wireless mouse no longer works, yet the Mighty Mouse does. Most frustratingly, my WD Passport external hard drive with my Time Machine on it, is no longer recognised. I have searched the Internet and there seem to be literally hundreds of people who are suffering a variety of frustrations from Yosemite. I've tried a few of the 'solutions' based on the 'turn it off and turn it back on again' theme, all to no avail. Having bought Macs since the early 1990s, I've always championed their simplicity and reliability. My patience is being sorely tested by Yosemite. A cheap PC with the new Windows operating system is beginning to look like an attractive alternative, especially now that Yosemite is looking like Apple's version of "Vista".

Any helpful ideas would be very welcome.