AOL seems to have a problem installing on multi-core Intel Macs: The installation hangs at "Installing Main Database." I found a successful workaround for this problem. Go to Apple's developer website and download the CHUD tools (Tools Download page; direct download [32mb]).
Once installed, there will be a Processor preference pane in System Preferences. Use this to turn off all but one processor, then run the AOL installer. Once the installer finishes, turn the processors back on.
[robg adds: I haven't tested this one, but I seem to recall that disabling CPUs solved install issues with other apps.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070605225508893