audio works in VC but not in an xterm

[Andras Simon]

This is an up-to-date, PulseAudio-less F18/Xfce running on an eeepc.
In an xterm, mplayer -ao alsa ... says

[AO_ALSA] alsa-lib: confmisc.c:768:(parse_card) cannot find card '0'
[AO_ALSA] alsa-lib: conf.c:4246:(_snd_config_evaluate) function
snd_func_card_driver returned error: Permission denied
[AO_ALSA] alsa-lib: confmisc.c:392:(snd_func_concat) error evaluating strings
[AO_ALSA] alsa-lib: conf.c:4246:(_snd_config_evaluate) function
snd_func_concat returned error: Permission denied
[AO_ALSA] alsa-lib: confmisc.c:1251:(snd_func_refer) error evaluating name
[AO_ALSA] alsa-lib: conf.c:4246:(_snd_config_evaluate) function
snd_func_refer returned error: Permission denied
[AO_ALSA] alsa-lib: conf.c:4725:(snd_config_expand) Evaluate error:
Permission denied
[AO_ALSA] alsa-lib: pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM default
[AO_ALSA] Playback open error: Permission denied
Failed to initialize audio driver 'alsa'
Could not open/initialize audio device -> no sound.
Audio: no sound

But the same works in a virtual console (even while X is running).
Is there something I could check?

Andras