No WLAN via Aspire 5002WLMi 11.10 - 3.0.4-generic

Lets see what firmware you presently have on your system -- please type the following in a terminal:
ls /lib/firmware/b43
ls /lib/firmware/b43-open

If you see ...fw files in the .../b43 directory, you have the Broadcom firmware, and should be all set. If you do not see files or the .../b43 directory does not even exist, then install it with a completely fresh install of the b43-fwcutter package (and watch your syntax, your above command was wrong on the typeo firmware package.
sudo apt-get purge b43-fwcutter
and when connected with a wire to the internet:
sudo apt-get install b43-fwcutter
and accept the download offer.

If you have the firmware, then check for the following exact line in any file in /etc/modprobe.d
blacklist b43
You may use grep to easily check:
grep "b43" /etc/modprobe.d/*

Delete any such lines found -- and disable/enable wireless or reboot.

Look for the b43 modules in the output of lsmod, it should be there, and you should not see the wl module.
All the above assumes you really have a Broadcom chip.
The firmware-b43-installer package (note the second hyphen) will work for some broadcom chips, another package, firmware-b43-lpphy-installer works for others. Neither is necessary if you have the proprietary Broadcom firmware (correct version hopefully selected automatically for you at the download).

ubuntu@ubuntu-Aspire-5000:~/rtl2832u-new-3.0$ sudo ls /lib/firmware/b43
a0g0bsinitvals5.fw lcn0initvals26.fw lp1initvals20.fw pcm5.fw ucode19.fw
a0g0bsinitvals9.fw lcn1bsinitvals24.fw lp1initvals22.fw sslpn0bsinitvals16.fw ucode19_sslpn.fw
a0g0initvals5.fw lcn1bsinitvals25.fw lp2bsinitvals19.fw sslpn0initvals16.fw ucode19_sslpn_nobt.fw
a0g0initvals9.fw lcn1bsinitvals26.fw lp2initvals19.fw sslpn1bsinitvals20.fw ucode20.fw
a0g1bsinitvals13.fw lcn1initvals24.fw n0absinitvals11.fw sslpn1bsinitvals27.fw ucode20_sslpn.fw
a0g1bsinitvals5.fw lcn1initvals25.fw n0bsinitvals11.fw sslpn1initvals20.fw ucode20_sslpn_nobt.fw
a0g1bsinitvals9.fw lcn1initvals26.fw n0bsinitvals16.fw sslpn1initvals27.fw ucode21_sslpn.fw
a0g1initvals13.fw lcn2bsinitvals24.fw n0bsinitvals17.fw sslpn2bsinitvals17.fw ucode21_sslpn_nobt.fw
a0g1initvals5.fw lcn2bsinitvals25.fw n0bsinitvals22.fw sslpn2bsinitvals19.fw ucode22_mimo.fw
a0g1initvals9.fw lcn2bsinitvals26.fw n0bsinitvals24.fw sslpn2initvals17.fw ucode22_sslpn.fw
b0g0bsinitvals13.fw lcn2initvals24.fw n0bsinitvals25.fw sslpn2initvals19.fw ucode24_lcn.fw
b0g0bsinitvals5.fw lcn2initvals25.fw n0initvals11.fw sslpn3bsinitvals21.fw ucode24_mimo.fw
b0g0bsinitvals9.fw lcn2initvals26.fw n0initvals16.fw sslpn3initvals21.fw ucode25_lcn.fw
b0g0initvals13.fw lcn400bsinitvals33.fw n0initvals17.fw sslpn4bsinitvals22.fw ucode25_mimo.fw
b0g0initvals5.fw lcn400initvals33.fw n0initvals22.fw sslpn4initvals22.fw ucode26_mimo.fw
b0g0initvals9.fw lp0bsinitvals13.fw n0initvals24.fw ucode11.fw ucode27_sslpn.fw
ht0bsinitvals26.fw lp0bsinitvals14.fw n0initvals25.fw ucode13.fw ucode29_mimo.fw
ht0bsinitvals29.fw lp0bsinitvals15.fw n16bsinitvals30.fw ucode14.fw ucode30_mimo.fw
ht0initvals26.fw lp0bsinitvals16.fw n16initvals30.fw ucode15.fw ucode32_mimo.fw
ht0initvals29.fw lp0initvals13.fw n18bsinitvals32.fw ucode16_lp.fw ucode33_lcn40.fw
lcn0bsinitvals24.fw lp0initvals14.fw n18initvals32.fw ucode16_mimo.fw ucode5.fw
lcn0bsinitvals25.fw lp0initvals15.fw n1bsinitvals20.fw ucode16_sslpn.fw ucode9.fw
lcn0bsinitvals26.fw lp0initvals16.fw n1initvals20.fw ucode16_sslpn_nobt.fw
lcn0initvals24.fw lp1bsinitvals20.fw n2bsinitvals19.fw ucode17.fw
lcn0initvals25.fw lp1bsinitvals22.fw n2initvals19.fw ucode17_mimo.fw
ubuntu@ubuntu-Aspire-5000:~/rtl2832u-new-3.0$

ubuntu@ubuntu-Aspire-5000:~/rtl2832u-new-3.0$ sudo ls /lib/firmware/b43-open
ls: Zugriff auf /lib/firmware/b43-open nicht möglich: Datei oder Verzeichnis nicht gefunden
> b3-open NOT found

ubuntu@ubuntu-Aspire-5000:~$ grep "b43" /etc/modprobe.d/*
/etc/modprobe.d/blacklist.conf:# replaced by b43 and ssb.
-- I changed line to :
# replaced by b43 and ssb.
#blacklist bcm43xx

I will now reboot and get back to you.

After reboot now, NO Wlan-LED is on anymore and can't be switched on either :-(

ubuntu@ubuntu-Aspire-5000:~$ lsmod
Module Size Used by
bnep 18012 2
bluetooth 147156 7 bnep
parport_pc 32578 0
ppdev 12869 0
binfmt_misc 17374 1
snd_intel8x0 33449 2
snd_ac97_codec 106029 1 snd_intel8x0
ac97_bus 12642 1 snd_ac97_codec
snd_pcm 81557 2 snd_intel8x0,snd_ac97_codec
snd_seq_midi 13170 0
ir_lirc_codec 12739 0 [permanent]
lirc_dev 18670 1 ir_lirc_codec,[permanent]
snd_rawmidi 25327 1 snd_seq_midi
ir_mce_kbd_decoder 12635 0 [permanent]
ir_sony_decoder 12462 0 [permanent]
snd_seq_midi_event 14475 1 snd_seq_midi
ir_jvc_decoder 12459 0 [permanent]
snd_seq 51702 2 snd_seq_midi,snd_seq_midi_event
ir_rc6_decoder 12459 0 [permanent]
snd_timer 29140 2 snd_pcm,snd_seq
arc4 12473 2
ir_rc5_decoder 12459 0 [permanent]
snd_seq_device 14160 3 snd_seq_midi,snd_rawmidi,snd_seq
ir_nec_decoder 12459 0 [permanent]
b43 327277 0
snd 56294 11 snd_intel8x0,snd_ac97_codec,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device
dvb_usb 27654 0
pcmcia 40366 0
dvb_core 94027 1 dvb_usb,[permanent]
rc_core 21200 8 ir_lirc_codec,ir_mce_kbd_decoder,ir_sony_decoder,ir_jvc_decoder,ir_rc6_decoder,ir_rc5_decoder,ir_nec_decoder,dvb_usb,[permanent]
joydev 17679 0
soundcore 12600 1 snd
snd_page_alloc 14108 2 snd_intel8x0,snd_pcm
mac80211 271515 1 b43
shpchp 32421 0
cfg80211 169178 2 b43,mac80211
psmouse 69992 0
yenta_socket 27501 0
pcmcia_rsrc 18416 1 yenta_socket
serio_raw 13094 0
i2c_sis96x 12743 0
k8temp 12905 0
pcmcia_core 21573 3 pcmcia,yenta_socket,pcmcia_rsrc
lp 13412 0
parport 41188 3 parport_pc,ppdev,lp
usbhid 42613 0
hid 77797 1 usbhid
ssb 51198 1 b43
sis900 26830 0
ubuntu@ubuntu-Aspire-5000:~$

ubuntu@ubuntu-Aspire-5000:~$ lsmod | grep b43
b43 327277 0
mac80211 271515 1 b43
cfg80211 169178 2 b43,mac80211
ssb 51198 1 b43
ubuntu@ubuntu-Aspire-5000:~$

Very strange -- it works again -- I went back to the commands :
sudo apt-get update
sudo apt-get --purge remove firmware-b43legacy-installer bcmwl-kernel-source
sudo apt-get install b43-fwcutter firmware-b43-installer
- rebootet and voilá - the WAN LED is blinking again and I also got an IP again.
By writing this, I am not connected to the wire anymore :-)
Even though I think, the WAN-link should stay on permanent and not be blinking each 1-second
This may still be issue

Good as long as it's working, but you should not have commented out the #blacklist bcm43xx line.

Well, I took the comment out again, before I typed in the above 3 commands.
Therefore, I would say, we can mark this question as solved :-)
Thank you very much for your support.