We duplicated the problem using the Apple Telephone Tool v2.3.3 with Apple Printer Utility v2.0 under Mac OS 7.5.3, when the Macintosh was connected to the network using LocalTalk. When we tested the software using EtherTalk, we did not encounter any difficulties.
After sending or receiving a fax with the Apple Telephone Tool using a GeoPort Adapter, you may encounter system hangs when using the Apple Printer Utility, or after using the Apple Printer Utility when you Restart or Shut Down. Even if you disable the Apple Telephone Tool and fax extensions using the Extensions Manager, and restart your Macintosh, you may still encounter hangs after using Apple Printer Utility.
Until this problem is isolated and fixed, when you are using a LocalTalk network connection, you should refrain from using the Apple Printer Utility and the Apple Telephone tool when using LocalTalk on the same Macintosh computers using Mac OS 7.5.2 or 7.5.3.