I recently upgraded my system from Fedora 17 to Fedora 18, and afterwards Evolution 3.6 (using the evolution-rss plugin) had an empty list of feeds in edit/preferences/news+blogs.

Thanks to Lucian Langa who pointed me to a manual migration script, which fixed the issue for me.

In order to compile and use it:
- download and save the migration script

- make sure you have packages gcc, GConf2-devel and gtk2-devel installed (you might need additional packages to compile it)

- open a terminal and change to the directory where you saved the .c file and run the following command:

gcc `pkg-config --cflags gtk+-2.0` `pkg-config --cflags gconf-2.0` `pkg-config --libs gtk+-2.0` `pkg-config --libs gconf-2.0` -o evolution-rss-migrate-feeds evolution-rss-migrate-feeds.c

- if no errors are shown, you should now have the executable. Check using

ls -l evolution-rss-migrate-feeds

- quit evolution. Now run the migration script

./evolution-rss-migrate-feeds

(no output will be printed)

- Start evolution, go to edit/preferences/news+blogs, and you should now see the feeds that you had configured in evolution 3.4.x prior to the upgrade