I had aslo problems with my latpot.

Try it:

blog.professorcoruja.com.br/.../como-fazer-o-wifi-broadcom-bcm4318-do\
.html

In English:
ubuntuforums.org/showthread.php+presario+v2000

floppyjoes.homeip.net/phpBB2/viewtopic.php?t=5

Well, what kind of wireless card is it? Does Ubuntu recognize it at
all, even under the Restricted Drivers Manager? What release of Ubuntu
is it?

Myself, my card is an Ativa PCMCIA card that is a rebranded Atheros card
and the restricted driver (ath_hal) does not work. I had to use
ndiswrapper, which was surprisingly easy to get working.

Are you trying to do this via the command line or via Gnome?

What I did, was install the ndiswrapper which uses the windows drivers of your
wireless card, and then when the ndiswrapper was working properly, I installed
the Wifi-radar to manage the connections.

You can download the ndiswrapper from this link:
http://ndiswrapper.sourceforge.net/joomla/ and follow the instructions.

And the Wifi-radar install it from synaptic.

click on the little computer icon on the top bar. it represents
the connection. then click on CONFIGURE. it will compure for a minute
or two, then give you a new box. highlight the wireless connection and
click on properties. it will give you a dropdown box to select the
wireless connection and a lower box to type in the password if you need one.
im doing that from memory, so someone please correct me if i miss spoke.
also, you can save your settings using the LOCATION box at the top of
the configure window. i dont know why they don't call that SAVE
CONNECTION SETTINGS, but they call it LOCATION instead.

Is there any special software like that which I could use for a fiberlink ? I
still cannot connect under Ubuntu. I can connect under Windows and Mandriva.

If its a broadcomm wireless adapter, the following link could help you

http://www.ravisblog.com/?p=70

To solve these Wireless problems with laptops and Broadcom chips, you
can also buy on of these PCMCIA wireless cards and disable the
internal Broadcom wireless device. I have a Dell Latitude D600, which
came with an internal wireless mini-pci card, with Broadcom chips.
This didn't work with Linux so I acquired a Cisco wireless adapter,
which was perfectly recognized by Ubuntu.The card will also give you
better coverage, as the antenna is situated on the bit sticking out.