AOL 3.0 installs the AOL Link extension, which conflicts with the Apple Internet Dialer.
Here are some workarounds:
If you no longer want to use AOL 3.0
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Click and drag the AOL Link extension from the Extensions folder to the desktop, restart the computer, and try the Apple Internet Dialer again. Removing the AOL Link extension does not disable AOL entirely, but it does nullify the benefits of the AOL Link extension.
If you want to continue using AOL 3.0
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Insert a tilde(~) character at the beginning of the extension name, for example, ~AOL Link. When you want to use AOL, an error message appears indicating that AOL Link needs to load first, AOL will then make the needed changes (requiring a couple computer restarts) and then let you proceed. At the end of the AOL session, AOL will ask if you want to restore your provider information to it's original configuration -- select yes, restart the computer and the Apple Internet Dialer should function normally.