I've been using Plaxo for about two months, and always wondered why I couldn't see my calendar, notes, and tasks. It would say how many items I had in each folder, but just blank days and pages when I went to a date. Then I found the Plaxo Toolbar for Thunderbird, and found in downloading that, it required Firebfox to download correctly. Once that was done, in Firefox I can now see the calendar, notes, and tasks. Safari will run MyPlaxo and the Contacts and Business Card pages OK, but not the other elements.
[robg adds: I'm not a Plaxo user, so I can't test this one...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051001005221755