USB Ports Not Working

I'm posting this as an open question as this one has me stumped. I have a Dell Inspiron 537S mini desktop. The USB ports are not working properly. The only one that stays working is the one for the mouse. I've tried replacing the keyboard and it doesn't work. Updated drivers, firmware which does help momentarily but then goes back to being inoperable. Not sure if replacing whole motherboard would do the trick or even solve the problem. If anyone has a suggestion I'm open to it. Thanks ahead of time.