Looks like the plugins are now statically linked into libasound instead of dynamically loaded from /usr/lib/alsa-lib/. I know I had that directory full of *.so's related to alsa on another comp.
(Unless I'm seeing things and it never was done this way :P)

Since it fails in snd_pcm_open_conf and plugins are usually loaded in the config files. Do you maybe have an old /etc/asound.conf or ~/.asoundrc lying around?