Comment 2 for bug 1208224

Is your /usr on a separate partition from / ?

It appears that sometime between lucid and precise, the libdrm2 package regressed, and is now installing its library to /usr/lib/$arch instead of to /lib (or /lib/$arch). This means that for any system with /usr on a separate partition, plymouth will fail to start up correctly at boot time. This is probably the explanation for the problem you're seeing.

The issues with the x11.so backend are ignorable. You're not running an X server, so it's not as though this backend would be selected anyway - you should probably just remove the plymouth-x11 binary package from your system, which is not installed by default.