Instead of using iSync to import an iCal .ics to Maemo Calendar, try GPE Calendar. The alternative GPE Calendar app handles the import fine, and exports a .ics file that Maemo's native Calendar app can deal with. I just posted detailed instructions on my blog.

Basically, install GPE Calendar, have it import the .ics file, run the command line command gpe-calendar -e filename.ics and open that in File Manager to get your events correctly imported into Maemo Calendar.