Mac OS X 10.1: "The Classic Environment is Not Responding" Message

Symptom

After clicking Stop in the Classic pane of System Preferences, an alert box appears with this message:

"The Classic Environment is Not Responding. You may click Cancel and attempt to save any changes to open documents..."

Note: This issue may occur with certain computers when Mac OS X 10.1 and the Mac OS 9.2.1 System Folder used as the Classic startup System Folder are on different volumes.

Solution

Update to Mac OS X 10.1.2 or later. Use the Software Update pane of System Preferences, or download the update from Apple Software Downloads (http://www.apple.com/swupdates/).