I just noticed I posted to your other thread for the same issue. Let's just stick to this thread from now on. What devices are you trying to use, and how many different devices? Have you taken a single USB device, like your mouse and tried to plug into each one, one at a time, to see if only one of them is failing?
Regarding the MSI 550ti, my friend uses that same one and to be honest, I just liked the looks of it and like MSI so on his recommendation I gave it a shot. I'm not a gamer at all, so I knew it could handle anything I was doing. I just wanted a good low cost card because I didn't want to put the extra work on my CPU by using integrated graphics. The EVGA is best rated version of the 550ti, so depending on the intensity of the games you're playing you should be fine. My friend plays all of the big name popular games and I've never heard him say the card couldn't handle it.