Amarok crashes everytime I search in the ogg-files (500kbps) I have ripped myself. Seems to be a gstreamer-problem as gdb said this:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1231606864 (LWP 24829)]
0xb7350b03 in gst_ogg_demux_get_type () from /usr/lib/gstreamer-0.8/libgstogg.so

Should I report a bug on gstreamer, amarok or am I doing something wrong?

Yes, sounds like a GStreamer bug.