> Can anyone help, please?

Nobody?

blub ...

Open terminal, run alsaplayer and mplayer at commandline as root.
Successfully play a data CD/DVD with mp3 files and DVD video disk with DVD video.
Now attempt to do the same as user tux.
What are the errors ?

If it's a one user environment, run it as root. That doesn't excuse the problem, it shouldn't happen but make your life easier...

Thanks for your replies, Mojo, andu. I'M NOT SHOUTING ... I'M JUST WRITING THIS IN CAPITALS SO THAT MY COMMENTS ARE EASIER TO DISTINGUISH FROM THE TERMINAL OUTPUT THAT FOLLOWS.

OK, THIS IS WHAT HAPPENS WHEN I PLAY AN AUDIO CD WITH ALASPLAYER STARTED FROM THE TERMINAL AS ROOT. AS SOON AS I CLICK ON ALSAPLAYER'S DISK BUTTON STAN GETZ BEGINS TO PLAY THE SAXOPHONE. GREAT!

tux@slitaz:~$ su
Password:
root@slitaz:/home/tux# alsaplayer
root@slitaz:/home/tux#
root@slitaz:/home/tux# exit

AND THIS IS WHAT HAPPENS WHEN I PLAY THE SAME AUDIO CD WITH ALASPLAYER STARTED FROM THE TERMINAL AS TUX. EACH TIME I CLICK ON ALSAPLAYER'S DISK BUTTON THE SAME ERROR MESSAGE POPS UP ...

tux@slitaz:~$ alsaplayer
CDDA: error opening device /dev/cdrom
CDDA: error opening device /dev/cdrom
CDDA: error opening device /dev/cdrom
tux@slitaz:~$


HERE'S THE SAME BUT THIS TIME WITH A VIDEO DVD. FIRST MPLAYER (GMPLAYER) IS STARTED FROM THE TERMINAL AS ROOT. I CAN WATCH THE FILM WITHOUT A PROBLEM ...

tux@slitaz:~$ su
Password:
root@slitaz:/home/tux# gmplayer
MPlayer 1.0rc2-4.4.1 (C) 2000-2007 MPlayer Team
CPU: Intel(R) Pentium(R) D CPU 2.80GHz (Family: 15, Model: 6, Stepping: 4)
MMX supported but disabled
MMX2 supported but disabled
SSE supported but disabled
SSE2 supported but disabled
CPUflags: MMX: 0 MMX2: 0 3DNow: 0 3DNow2: 0 SSE: 0 SSE2: 0
Compiled for x86 CPU with extensions:
mplayer: could not connect to socket
mplayer: Connection refused
Failed to open LIRC support. You will not be able to use your remote control.

Playing dvd://1.
There are 5 titles on this DVD.
There are 40 chapters in this DVD title.
There are 1 angles in this DVD title.
audio stream: 0 format: ac3 (mono) language: en aid: 128.
audio stream: 1 format: ac3 (mono) language: de aid: 129.
audio stream: 2 format: ac3 (mono) language: it aid: 130.
audio stream: 3 format: ac3 (mono) language: fr aid: 131.
audio stream: 4 format: ac3 (mono) language: es aid: 132.
audio stream: 5 format: ac3 (mono) language: en aid: 133.
number of audio channels on disk: 6.
subtitle ( sid ): 0 language: en
subtitle ( sid ): 1 language: fr
subtitle ( sid ): 2 language: pt
subtitle ( sid ): 3 language: da
subtitle ( sid ): 4 language: fi
subtitle ( sid ): 5 language: sv
subtitle ( sid ): 6 language: no
subtitle ( sid ): 7 language: de
subtitle ( sid ): 8 language: nl
subtitle ( sid ): 9 language: cs
subtitle ( sid ): 10 language: pl
subtitle ( sid ): 11 language: tr
subtitle ( sid ): 12 language: hu
subtitle ( sid ): 13 language: bg
number of subtitles on disk: 14
MPEG-PS file format detected.
VIDEO: MPEG2 720x576 (aspect 2) 25.000 fps 9800.0 kbps (1225.0 kbyte/s)
==========================================================================
Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough
VDec: vo config request - 720 x 576 (preferred colorspace: Mpeg PES)
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
The selected video_out device is incompatible with this codec.
Try appending the scale filter to your filter list,
e.g. -vf spp,scale instead of -vf spp.
VDecoder init failed :(
Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b
Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2))
==========================================================================
==========================================================================
Opening audio decoder: [liba52] AC3 decoding with liba52
No accelerated IMDCT transform found
No accelerated resampler found
AUDIO: 48000 Hz, 2 ch, s16le, 96.0 kbit/6.25% (ratio: 12000->192000)
Selected audio codec: [a52] afm: liba52 (AC3-liba52)
==========================================================================
AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample)
Starting playback...
VDec: vo config request - 720 x 576 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
VO: [xv] 720x576 => 768x576 Planar YV12
A: 49.1 V: 49.2 A-V: -0.010 ct: 0.091 1223/1223 13% 2% 0.8% 0 0

Exiting... (Quit)
root@slitaz:/home/tux#
root@slitaz:/home/tux# exit

... AND THIS IS WHAT HAPPENS WITH THE SAME DVD IN THE DRIVE BUT THIS TIME GMPLAYER IS STARTED FROM THE TERMINAL AS TUX ...

tux@slitaz:~$ gmplayer
MPlayer 1.0rc2-4.4.1 (C) 2000-2007 MPlayer Team
CPU: Intel(R) Pentium(R) D CPU 2.80GHz (Family: 15, Model: 6, Stepping: 4)
MMX supported but disabled
MMX2 supported but disabled
SSE supported but disabled
SSE2 supported but disabled
CPUflags: MMX: 0 MMX2: 0 3DNow: 0 3DNow2: 0 SSE: 0 SSE2: 0
Compiled for x86 CPU with extensions:
mplayer: could not connect to socket
mplayer: Permission denied
Failed to open LIRC support. You will not be able to use your remote control.

Playing dvd://1.
Couldn't open DVD device for writing, changing DVD speed needs write access.
Couldn't open DVD device: /dev/cdrom
No stream found to handle url dvd://1

Exiting... (Quit)
tux@slitaz:~$

THE SAME HAPPENS WITH OTHER APPLICATIONS THAT WANT TO ACCESS THE CDROM DRIVE, LIKE BURNBOX OR ASUNDER. I JUST MADE A LITTLE EXPERIMENT AND PUT THE LIVE CD OF FEDORA 13 INTO THE DRIVE ... IT IMMEDIATELY BEGAN TO SPIN AND A SECOND OR TWO LATER SHOWED UP IN PCMANFM. ONE CLICK AND THE CD WAS MOUNTED AND COULD BE READ AND ANOTHER CLICK AND THE CD EJECTED. WHEN I DO THE SAME WITH ANY OF MY AUDIO CDs OR DVDs NOTHING AT ALL HAPPENS ...

Check /etc/fstab
/dev/cdrom /media/cdrom iso9660 user,ro,noauto 0 0
Comment out with #
#/dev/cdrom /media/cdrom iso9660 user,ro,noauto 0 0

Sorry for the late reply, Mojo. I was away for a couple of days. I have now figured out what's been wrong with the CD/DVD drive. The reason for the troubles was that there's no hard drive in my PC. The CD/DVD drive is the first and the only drive which means that the system automatically assigned it to dev/hda which was "root:disk". When I make dev/hda part of the cdrom group everything is fine. To make the change permanent I added a line at the bottom of /etc/init.d/rcS right above "# Display and log boot time" ...

# Change hda group from "root:disk" to "root:cdrom"
chgrp cdrom /dev/hda

... not sure, though, if rcS is the right place to do something like that. I've just discovered that there's /etc/init.d/local.sh which would probably have been a better place. But with a system like mine every change of that kind means that I have to burn yet another CDROM (rw) ...