What about your irc3480?
Have you solved the problem?
All the best
Sorry, I don't have an AR-FX10 manual. You can buy one here: http://www.justmanuals.com/sharp-digital-full-color-multifunctional-system-option-expansion-arfx10-parts-service-p-32801.html
There is no write protect switch on the ICU, so it must be on the fax PWB somewhere. Good luck =^..^=