Thunderbolt Display USB ports have stopped working

I think rebooting fixed this last time but I have too many apps and windows open that I don't want to lose my train of work. This affects my USB keyboard and mouse which I connect to the Thunderbolt Display because I don't need USB 3.0 speeds on those devices. Right now I reconnected them to a USB hub on my iMac. So does this mean I can no longer rely upon my USB 2.0 ports on my Thunderbolt Display? This is the second time this has happened, hence my vague recollection of rebooting fixing it last time and my reluctance to use rebooting again as it's a high price to pay in lost productivity.