ffmpeg conversion from wma to ogg does not work

Question

I'm trying to convert wma to ogg, using ffmpeg. However, both using the vorbis or libvorbis encoder (not sure which one I should use), this fails. Using arch linux.

ffmpeg -i test.wma -acodec vorbis test.ogg

Final part of output:

Stream mapping:
  Stream #0:0 -> #0:0 (wmav2 -> vorbis)
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

So I assume, Arch does not use vorbis but libvorbis (can't find much more about this in the documentation). So I try:

ffmpeg -i test.wma -acodec libvorbis test.ogg

Output:

Stream mapping:
  Stream #0:0 -> #0:0 (wmav2 -> libvorbis)
Press [q] to stop, [?] for help
[output stream 0:0 @ 0x8754860] 100 buffers queued in output stream 0:0, something may be wrong.
[libvorbis @ 0x8764640] Que input is backward in time
[ogg @ 0x8763f60] st:0 PTS: 15248 DTS: 15248 < 16321 invalid, clipping
[ogg @ 0x8763f60] st:0 PTS: 16272 DTS: 16272 < 16322 invalid, clipping
[libvorbis @ 0x8764640] Que input is backward in time
Que input is backward in time.95 bitrate=  11.6kbits/s    
[libvorbis @ 0x8764640] Que input is backward in time
Que input is backward in time.54 bitrate=   6.2kbits/s    
Que input is backward in time.09 bitrate=  38.3kbits/s    
Que input is backward in time.32 bitrate=  58.0kbits/s    
Que input is backward in time.10 bitrate=  68.0kbits/s    
[libvorbis @ 0x8764640] Que input is backward in time
[ogg @ 0x8763f60] st:0 PTS: 598508 DTS: 598508 < 598681 invalid, clipping
[ogg @ 0x8763f60] st:0 PTS: 598636 DTS: 598636 < 598682 invalid, clipping
Que input is backward in time.82 bitrate=  74.1kbits/s    
[libvorbis @ 0x8764640] Que input is backward in time
Que input is backward in time.62 bitrate=  77.1kbits/s    
Que input is backward in time.33 bitrate=  80.3kbits/s    
[libvorbis @ 0x8764640] Que input is backward in time
Que input is backward in time.92 bitrate=  83.7kbits/s    
[ogg @ 0x8763f60] st:0 PTS: 1157500 DTS: 1157500 < 1157898 invalid, clipping
Que input is backward in time.45 bitrate=  86.2kbits/s    

And this just continues indefinitely.

Note: I do have the libvorbis package installed.

Anybody any idea what is going on?