Problem retrieving RSS feed from WP blog to Joomla site

Hello to everyone.

On my Joomla 1.5 website I have mod_feed component, which loads rss feed from my WordPress blog (only messages of distinct category if this matters). I do not know why, but once it has stopped to load recent entries (it was working fine for more than a year, but then suddenly stops). Now on the website’s mod_feed the message dated by 1st of September is the topmost one, while there are three more recent messages in the blog (yes, they all belong to distinct category I mentioned above). When I copy feed URL (which is a wordpress address) from the mod_feed settings to the browser, I see all the entries, including the most recent. Any caching is switched off in Joomla and mod_feed. What can it be and how can I solve this? I think that problem is exactly on the WordPress side, because now I see another one important change: the site is being loaded really slow, unless I disable that mod_feed. So, it seem like a kind of problem in retrieving data from WP. And I do not think that this can be due to networking problems at least because site can retrieve older messages due from the blog… Can someone give me any recommendations?

Thanks beforehand.