The Installer disk installs a number of fonts (Postscript Type 3/True Type). I had problems with several of them. Courier, for example, displayed in Emailer as garbage. To try to fix this I removed the TrueType part of the font. This fixed my display problems but then I noticed that the new Courier had slightly different spacing than the old so I installed an old copy of Courier. This caused ATM to display the message "Cannot load due to lack of memory or resources." I reinstalled ATM from the printer CD to no avail. The solution was to install ATM from the Mac OS 8.5.x CD. The version of ATM on the LaserWriter CD, even though it has same version number (4.02) is apparently not the same.
My guess is that this is not a problem that all 8500 users will experience. But just in case it happens to you, now you know what to try.