I already tried to disable all plugins, and switched back to the standard theme.
I also switched from php4 to php5.
The last post in the feed dates to the 5.1.. Last update was 6.1. although there are posts till yesterday.
If you open the feed, it comes so quick, that it seems to me as it would be static.
Right now i don't habe any clue what the problem could be and would be very thankful, if anybody could give me a hint. Maybe just a location where i could look, why wordpress does think the feed doesn't need to update.
Thanks in advance