The version of America Online (AOL) originally bundled with the PowerBook 3400 is 3.0D. This version does not properly deal with the situation when another application, such as FAXstf, is set to answer. Upgrading to AOL version 3.0.1 or later will remedy the situation.
The 3400 was a bangin’ machine, but even the best computers of the 90s often fell to badly written AOL software.