Had this problem myself. Leave it for a few days and they should reappear.
Last time I had to reinstall AOL I went to favourites, manage, and clicked on Save my favourite places as a favourite file on my pc.
After the reinstall of AOL I loaded the favourite file from a cd I'd saved it to and all was well. Two days later my favourites had been reinstalled,from AOL I assume, so everything was duplicated.