It could be your usb ports have gone bad to. I had this happen on my dell 1545 laptop and I had tried reinstalling the drivers for4 it updating the bios to make sure it wasnt a problem with the bios. I then broke down and contacted dell about it and it seems that one of the usb ports had gone bad in it cause when i used the other ports it didnt have the problem of doing that. So if I was you I would be looking into my warranty and contacting toshiba