Here are a list of things to check and confirm if you're having trouble updating the RC-3 to its latest version:
-Be sure to connect the RC-3 directly to a USB port on the computer and not through a USB hub.
-Try a different USB cable.
-Try using a different USB port on the computer.
-Confirm that both the OUTPUT Rhythm and Loop knobs are in the "MIN" positions.
-Make sure you power on while continuing to hold down both the TAP TEMPO and WRITE buttons. Continue holding them until "UP" appears in the display. (Once "UP" is displayed, you can release the buttons).
-Make sure the update files are uncompressed, and then drag both of the .TXT and .BIN files to the RC-3's drive. Do NOT place them *inside* the Roland folder. After they have been transferred, you should see the Roland folder, the .TXT file, and the .BIN files together in the same window.