Symptom
When using the Multiple Users facility of Mac OS 9, and trying to open America Online 4.0, the following error message appears(see Figure 1):
"The America Online application cannot start up. The needed file 'Main Database' couldn't be opened."
Figure 1: America Online alert.
When opening America Online 3.0, it may appear to start and then quit with no error message.
Solution
The solution is to log in using the owner account for the computer, and move the whole America Online application folder to the Application Support folder within the System Folder. This will enable its use by all user accounts, with no other changes necessary.
If you have multiple copies of AOL installed on your hard drive, you may need to remove the additional copies. Keep only the one which you have placed in the Application Support folder.