I had the same problem. I added a feed and then the RSS reader would crash whenever I tried to refresh it. Unsubscribing also made it crash.

I fixed the problem by using Xterminal to edit the feedlist.opml file, which stores a list of your subscribed feeds. After removing the line with the offending feed, wha la! problem fixed.

The feedlist.opml file is stored in a hidden directory in your /home/user directory called .osso_rss_feed_reader. I edited the file using the built in text editor, vi. I had no idea how to use vi, but a handy web site gave me the basic commands (http://www.cs.rit.edu/~cslab/vi.html)