Did you just uninstall the driver or did you use the Driver Cleanup Utility available on the AMD Driver page? You need to use the cleanup utility before uninstalling the drivers (will uninstall them in the process) to do it correctly.
Yesterday I managed to get all of the cards to work, I just had to switch the third one to a 16x riser and connect my monitor to it. I used the 13.4 driver too.