I've been having a problem with my RSS feed, as well. I use Yahoo for my feed reader.
It's been 4 MONTHS since it's updated my RSS feed, which was just a regular RSS feed.
After reading here, I decided to try an Atom feed, and that works perfectly! I don't know if the problem is the feed, or the reader, but RSS doesn't work and Atom does.
I went to the Feed Validator, and this was the response:
This feed is valid, but interoperability with the widest range of feed readers could be improved by implementing the following recommendations.
* line 28, column 148: Unregistered link relationship: search [help]
... com/osd.xml" title="Shaking The Tree" />