Ahh, the issue there appears to be that the JFBCLike tag is being sucked into the meta description on your site, and then being replaced with the Like button. So, the meta description has a like button in it, and browsers don't know what to do with that there, so they just display it.. with the bad side effects that you're seeing.
For now, I'd recommend that on the K2 articles you're inserting the tag into the top of, that you set the Meta Description for that article in the admin area. This (I'm pretty sure) will prevent K2 from just taking the first paragraph and using that as the description. Alternatively, you can insert the JFBCLike tag at the bottom of the article.
I've taken a note of this issue in our bug tracker and will see if there's a way that we can prevent this behavior in a future release.
Hope this helps, but if you have any questions, issues, or suggestions, please let us know!