Chris, I stand corrected. The rule does not say you have to cross the Atlantic and the Pacific. I've modified my comment above accordingly.
Europe-Asia-SWPacific-Africa-Europe is not allowed because of the backtracking between SWPacific and Europe. Meanwhile, you can do a 3 continent OWE as Europe-Asia-Africa-Europe because you are allowed to back track Asia-Africa and Africa-Europe (asked AY and was told okay).

Also, you are allowed to have two intercontinental arrivals and departures for Asia. Therefore you can do a 4 continent OWE as Europe-x/Asia-SWPacific-Asia-Africa-Europe.
Asia-SWPacific-<transpacific flight>-NAmerica-<transpacific flight>-Asia is defined as a circle pacific flight. OWEs don't allow this. You can find circle pacific fares ex-Australia and ex-HKG if you're interested.
[This message has been edited by silver (edited 10-05-2000).]