I can't get the dial-backup feature to work with the RF300E.

Go to: http://www.multitech.com/en_US/SUPPORT/Families/RASFinder/firmware and download RASFinder RF300E firmware 1.08 or newer.
Locate your former install disc of the software. It's a good idea to know where it is in case you wnat to go back. Make any notes of your current setup. Use the Download Wizard Setup. Don't make any changes to the default screens. The only exception to this would be inserting IP addresses when prompted. After the Defaults have been restored uninstall the version you have been using. Install 108 and go through the setup. At the end of the setup do not upgrade or download defaults when the prompt comes up. Finish the install. Once the software is installed there is an Upgrade option. Use it to upgrade to 108 firmware. This should all be done over a serial connection with the command cable for best results.