After some searching I found a solution to my problem. Which was that my RSS name was so long, containing both the blog name and the post title. (problem fix: remove 'wp_title_rss()' from feed-rss2.php , feed-rss.php and feed-atom.php)
I have had the problem before and also I see loads of question on this subject. Now I am wondering what is the use of 'wp_title_rss()' in the RSS title? So many questions on the RSS feed are how to only have the blog name as the title.
So just for my understanding, can somebody explain why one would want to also add the title of each new post to be/complete the 'name' of the RSS feed?
And if there is no use to it, maybe it is a good suggestion to take it out?
The fix to my problem is in the core files, so I am somewhat hesitant to alter it. (have done it, but still) Maybe a good one for the admin settings? Under 'reading'it would be great. radiobuttons for title, or maybe even the option to put in the name in a textfield?
Looking forward to more insight :)