I have not tried to test this myself as yet, but three readers (Jens Rudnick, Neal Heacock and Claus Skrepe) independently report exactly the same unusual requirements to precipitate a Finder quit or crash: Start with a folder that has several other folders nested within it. Have all folders set to View "As List." Turn on Calculate Folder Sizes from the View Options window. The crash/quit will then typically occur when closing folders while holding the Option key, although it may happen at other times as well. Jens claims: "This only happened since converting one of my HD's to a
OS 8.1 HFS Plus volume."
Update: For Paul Barton, this problem was caused by having CoolViews 1.1 installed. Jean-Pierre Côté found that disabling AutoMenus Pro 3.5.1 solved the problem. However, I suspect these conflicts are not the cause for every user. Other readers suggested that enabling virtual memory eliminated the problem. Several readers noted that the problem is independent of whether or not you use HFS Plus.