I found this interesting post on the VDPAU mailing list: http://lists.freedesktop.org/archives/vdpau/2012-May/000022.html
The proposed patch can be applied to current Debian libvdpau sources (v0.4.1) and in my case allows the Flash plugin to work more or less as it worked before 11.2; the patch also provides a conffile in order to change its behaviour, just in case the current situation will change. Attaching the EXPERIMENTAL result. Mau
libvdpau_0.4.1-5.1.debian.tar.gz
Description: GNU Zip compressed data
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