17" studio display usb port not working

Apple Studio Display 17" M7649 usb ports stopped working--

When I go to about this mac it shows the port but doesnt acknowledge aanything plugged in.

Other hubs ( on the macG4 Quick Silver 933mhz)are showing up with chain of items keyboard and mouse .

But when mouse is plugged into back of monitor ---NUTTIN'

OB btw - this was working 3 or 4 days ago..it just started monday

Any insights???