Assuming the lock key on the back of the player is in the unlocked position, it sounds like there is a corrupt firmware file. This should just need a firmware reinstall.
Download the firmware install from the RCA website: http://voxrightnow.custhelp.com/app/answers/detail/a_id/2558
Follow the on-screen instructions to perform the install.
Be sure to back up any important media before performing this install.
If your computer does not recognize it, press and hold the play button while connecting the device for upwards of 30 seconds.