Error 403 with Google Analytics Link-Tagging

Hi there,

I am new to hosting my wordpress blog but I have encountered this issue:

Whenever I share a new blog-post through twitter with the help of the bit.ly-shortener, all users get a 403-error-message when clicking any link on my blog. I set up my twitter-feed to add some google analytics link-tagging which looks like (as you might know)
?utm_source=twitter&utm_medium=twitter-feed&utm_campaign=social+media&utm_content=new+blog+post.

The blog post itself is found and there are now problems for that. But as soon as someone will click a link in the sidebar, the header, or even leaves a comment, he will have the 403-error-page in respond. If I do not add the link-tagging, everything works fine.

You can try it yourself, this is one of that tweets with link-tagging.

What puzzles me most is, using the link-tagging code in the theme (see the links in the slideshow or the article-list at the bottom of the homepage or a single article does not cause this error.

So does anyone of you have a clue how I can use link-tagging on twitter and make the blog work?

Update
While writing this ticket, I auto-posted a link to my blog-post via twitter. So now the standard-feedburner link tagging is added to the link. It works fine now via twitter. The complete link is

https://www.blog-n.de/2010/06/01/molders-verlangert-bis-2013/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+BlockN+%28Block+N+-+Das+Blog+aus+dem+Fanblock+des+Frankfurter+Volksbankstadion%29&utm_content=Twitter

but

It seems that the running application and/or network or whatever adds the “&utm_content=”-string to the link. And Facebook’s now breaking the link.
https://www.blog-n.de/2010/06/01/molders-verlangert-bis-2013/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+BlockN+%28Block+N+-+Das+Blog+aus+dem+Fanblock+des+Frankfurter+Volksbankstadion%29&utm_content=FaceBook

Funny thing: if you change the &utm_content=FaceBook to &utm_content=Facebook it will work out fine again.

Same issue, different source, or what do you think? I would desparately like to use link-tagging, but just in last case, it is not on my behalf to change the string (or better: I dunno how).

thanx,
rob