The only thing I can think of that might have happened (other than a Wine bug) is GCC or GLIBC being upgraded by 'emerge world'. GCC --version says "gcc (GCC) 3.3.6 (Gentoo 3.3.6, ssp-3.3.6-1.0, pie-8.7.8)", while ls /lib/libc* says "libc-2.3.6.so".
Perhaps you can revert to 0.9.15 and rebuild with your newer gcc and glibc to see if those are causing the problem.
Good idea, just did that. That seems to work fine, so GCC / glibc is not the problem.
(I found that Portage doesn't activate the new GCC, it only installs it. So the only actual upgrade was to glibc, and that was a minor bump from 2.3.5 to 2.3.6 according to the install log.. Anyway.)
If not, git-bisect should help you find the offending changeset.
Doing that just now, thanks. (Takes forever, I wonder if "make clean" at each step is really necessary..)