>   Of all the updates, this is probably the one:
> 
> [2012-07-05 19:59] upgraded glibc (2.15-12 -> 2.16.0-1)
> 
>   Can somebody who know how glibc figures into the
> error below, please take a look at the glibc changes in
> (2.15-12 -> 2.16.0-1). The Arch link to the diffs (nicely
> laid out is):
> 

The glibc update makes sense as the cause with respect to your error message. Note: The next Slackware release is getting closer to release candidate status, but the last I read about that progress was the next release was not going to bump to glibc 2.16 because that would start a whole new round of stability and testing issues. I'm not saying glibc is buggy (could be), only that glibc 2.16 is different enough from 2.15 that some ABI breakage is possible or like the gcc 4.7 headaches, is more strict with respect to compiling.

Can you roll back glibc? That would not patch the problem but at least makes the cause knowable for patching.

Darrell