Problems with feeds - invalid rss feed content

Hi,

i have problems with generating rss-feeds from my site and didn´t find a solution in the forum. Hope someone can help me.

I want to make a feed of all of my blog-entries in my local-test-installation of Drupal 5.7 but if i copy the link http://localhost/xyz/blog/feed to one of my feed-readers i will get the error message: invalid rss feed content. The aggregator module is enabled and providing news-feeds from other sides work.

Strangely blog feeds of my other site http://localhost/zyx/blog/feed work. I have no clue what can be wrong. I am using also "views-RSS" und "RSS Remote Enclosure" for making feeds from some views but the blog is no view... it is from the normal blog-module. So every click to any of the rss-feed-icons and trying to import them to my feed-reader fails. Unfortunately i didn´t try exporting rss-feeds directly after installation and now i have created some new content-types and enabled modules and have no idea what to do.
I disabled cck and views to isolate the problem. But it didn´t help. Does someone have an idea to solve it?

Thanks
Schneewittchen