Hi Wolfgang,
In one of your previous e-mails you stated...
"A further complication is that my wi-fi adaptor, D-link DWA-131 (Realtek RTL 8192SU), is not correctly installed by Suse 12.1 or Mageia-2-x86-64"
I checked Ubuntu 12.04 (Unity) release and Debian V6.0.4 LIVE release (upgraded on-line to V6.0.5) and neither of these releases includes the drivers for the Realtek RTL 8192SU wireless LAN adapter.
The method I used to check was to look in the /lib/firmware/ folder for the directory RTL8192U, ...and I found it doesn't exist.
If you wish to install drivers for the Realtek RTL 8192SU / D-link DWA-131 then I suggest you refer to this Debian wiki page...
http://wiki.debian.org/rtl819x
The instructions and script for installation on Debian Squeeze (V6.0.x) are also suitable for Ubuntu (12.04).
The instructions suggest that the driver files are placed in /usr/local/lib/firmware/RTL8192U.
However, I didn't do this and I don't know if this works or not. What I did was to place the three driver related files (boot.img, data.img, and main.img) in /lib/firmware/RTL8192U
I used the installation script provided on the Debian wiki page, but I modified it slightly to be as follows...
# aptitude install unzip && exit
$ wget ftp://ftp.dlink.com/Wireless/dwa130_revC/Drivers/dwa130_revC_drivers_linux_006.zip
$ unzip dwa130_revC_drivers_linux_006.zip
$ su
# mkdir -p /lib/firware/RTL8192U
# cp rtl8192u_linux_2.6.0006.1031.2008/firmware/RTL8192U/* /lib/firmware/RTL8192U
If the USB Wireless LAN adapter doesn't immediately commence operation then reboot.
Regards, Ian.
PS: If you'd like to download the latest Debian LIVE iso image and burn it to a DVD to try it out or install it, then goto here...
http://cdimage.debian.org/debian-cd/current-live/amd64/iso-hybrid/
...and download, say,...
debian-live-6.0.4-amd64-gnome-desktop.iso 29-Jan-2012 12:12 1.1G
Note: This iso is currently V6.0.4, but once you've installed it, you can do an on-line update that will take your system to V6.0.5.