Update: Others have claimed the deleting Netscape's Preferences file fixes the problem.
File sharing cannot be enabled Regarding the inability to enable File Sharing (reported by some users last time), Al Tucker noted that the 8.1 Installer "had blitzed my computer name in the File Sharing control panel. Restoring that fixed the problem."
RAM disk disappears I know not everyone … Read more
"We are aware that there are some concerns with the new OS 8.1 and NetDoubler 1.5. We are currently testing NetDoubler with OS 8.1 and OT 1.3."
Do a clean install of ATM software after installing Mac OS 8.1.
Move ATM up in the loading order (such as by removing the ~ in front of its name).