Now I’m seeing this behavior on some posts, but not others (within the same blog). For example:
If I click the Send to Kindle button here, the popup appears, I log in, and I see the full post’s content within the popup (in other words, it works perfectly):
https://toc.oreilly.com/2013/04/goodreads-amazon-winners-and-losers.html
Now if I click the Kindle button on this article, I get the popup, log in, and get the dreaded “Waiting for Content…”:
https://toc.oreilly.com/2013/04/libraries-to-become-community-publishing-portals.html
I’m using Chrome 26.0.1410.43 (newest) on OS 10.8.3. The only extensions I have installed are Google PageSpeed Insights and 1Password, both of which are disabled.