You can find that your own Blog is suffering some Feeds problems after updating to a newer WordPress version.
I’ve been able to resolve them, as far as I know, using this simple procedure.

How to fix it

• don’t insert withe/empty lines at the start end of confing and functions files; functions is a Theme specific file; check if you have one in your own Theme folder.
• go to all plugins that have an option-page and update them saving again their own settings.
• go to Settings and save again every section.
• refresh Permalinks.

Hope it helps!