Hi Ann, If Chimera used to work for you, and now the same version is crashing, this suggests it is having a problem with something saved in your Chimera preferences file. The Chimera preferences file is saved in ~/.chimera/preferences I suggest you try renaming this preferences file to preferences-old. If the preferences file is the problem Chimera will then start and it will create a new preferences file. We would like to fix the problem. Could you start the Mac Applications/Utilities/Console and see what it displays when Chimera crashes? If it gives an error message could you copy and paste it in an email to us? Also if you press the Logs button on the Console dialog, click the arrowhead for ~/Library/Logs and then the arrowhead for CrashReporter and then python2.3.crash.log. This will show detailed information about where Chimera crashed that would help us also. Thanks, Tom