one arduino not recognized

hi all,i have a question for anyone who can help,i have three uno's and a mega arduino,one of my uno's had grbl loaded,but did not have the G38.2 command for tool tip probe,so i got Grbl 1.1f and also updated my IDE,the Grbl was a zip,so i unpacked it and opened it up down through all sub folders to a Grbl loader,double clicked and the arduino IDE with Grbl sketch appears,uploaded it,but it could no longer see my uno,and when i plug the uno in to the same usb i get three mono tone beeps,as opposed to the usual low-high tone when connecting to usb,it does give the high-low tone when unplugging,so i expect the device is reccognized,but not fully accessible,my other unos and my mega are fine,they were chinese clones,i installed usb drivers for CH341SER driver and a driver toolkit installer,as this was needed for two of them,the one now not being read is one of them,so this is a pickle to say the least.
Any help would at least serve to eliminate future problems,seeing as the uno cost about 5 pounds i can't say i'm terribly bothered,but i can't have an on going sittuation where the uno's are disposable.