The SSL library does not seem to be the issue. I've checked and had the same ldd ouput with Firefox v. 17. Rather, the problem appears to be the libc version. (See mirabilos' comment at the lwn announcement.)
There goes the last Blogger compatible Browser. It does not appear to be a problem with the update, as I first thought. Downloading a fresh installation did not change anything with the issue.
I'm not sure, whether downloading the older Version 17 is a proper fix, either. Does Firefox provide 17.x security updates? I fear they might not.
Hence for now, sadly, it seems Opera is now the only modern browser still compatible with my old system... Don't get me wrong, I really like Opera, it's usually the fastest browser in my experience. But it's simply not as compatible as Firefox with some websites, and not properly supported by most Google services (Blogger, Mail, ...). I'm using the plain HTML interface with Google Mail when I'm in Opera. It's not pretty, but surprisingly fast.
Oh and - before people complain - trust me: I have good reasons for still running an old system... just click on the poulsbo tag.