**** LATEST UPDATE (June 13th 2012)**

I can't figure out what's wrong with my codes.
When I want to share one of my blog posts and use either the Facebook share button or copy the link of the blog post directly into Facebook all that pops up is the URL itself, not the meta info such as description or featured image!
I filled out the meta data for each and every post and I also added Open Graph to my code.

Yet, when I try to share my blog post links on Facebook, neither the meta description nor a thumbnail would show up for the majority of my blog posts. It's like something is blocking the information. I've run out of ideas. I really hope you guys can help me figure out what's wrong!
(obvioulsy I replaced the fillers above with my own data!)

I also used the Facebook Debugger and all it tells me is:

> Can't Download:	Could not retrieve data from URL.

An example for a blog post that can't be shared properly: http://zoomingjapan.com/favorite-photos/yumebutai/

There are very few blog posts that work with Facebook.
If I copy the URL of one of those into the Debugger I still get an error message, though:

> Object Invalid Value:	Object at URL
> 'http://zoomingjapan.com/travel/mount-koya-travel-report/' of type
> 'article' is invalid because the given value '377035309011137' for
> property 'fb:admins' could not be parsed as type 'fbid'.

The URL above is that of a blog post that could be shared properly, but yet gets an error message.

Thanks to Milo I was able to figure out that it has actually to do with my theme.
When I change the theme it suddenly works!
My parent theme can share properly, too: http://wordpress.site5.net/alltuts/
So, now I try to figure out WHAT in my theme is causing this error. I have no idea how to figure that out. Any ideas? :/

I replaced the **header.php, footer.php, single.php** and the **function.php** (which were the most suspicious to me) with the ones of the TwentyEleven theme of Wordpress. The problem stayed.
This means it must be another theme file that is causing those issues. I keep searching for it, but I really don't know what I'm looking for :(

Here's my htaccess file: http://pastebin.com/p4dRk0Gq


**Updated Information:**
I tried to replace one file after another again. Nothing.
However, I noticed something else!
When switching themes it works fine with **TwentyEleven**, but I have the exact same issue with the **TwentyTen** theme!
Maybe that gives us a clue where to search?? What's the big difference between those two themes?
I'm really desperate and refuse to believe that there is no solution for this issue!

Here's my header.php: http://pastebin.com/EPuNLtvH

Please help me out here!
Thanks a lot in advance for any advice you can give me.