This is due to Amarok not calling XInitThreads() which is required when multiple threads in the same process use Xlib.
As a (poor) alternative, Phonon-VLC would need to pass "--no-xlib" to libvlc_new(). However this would disable some useful Xlib-dependent plugins inside of LibVLC. Or Phonon-VLC could explicitly depend on LibVLC >= 1.1.6, which automatically but unreliably detects the need for "--no-xlib". Anyway, functionality will still suck due to avoiding Xlib.
This is due to Amarok not calling XInitThreads() which is required when multiple threads in the same process use Xlib.
As a (poor) alternative, Phonon-VLC would need to pass "--no-xlib" to libvlc_new(). However this would disable some useful Xlib-dependent plugins inside of LibVLC. Or Phonon-VLC could explicitly depend on LibVLC >= 1.1.6, which automatically but unreliably detects the need for "--no-xlib". Anyway, functionality will still suck due to avoiding Xlib.
In any case, this is not a VLC bug.