dmesg nach Einstecken lieferte:

[  118.759023] usb 1-3: USB disconnect, device number 3
[  125.592039] usb 1-3: new high-speed USB device number 4 using ehci-pci
[  125.725767] usb 1-3: New USB device found, idVendor=0b05, idProduct=17ba
[  125.725775] usb 1-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  125.725780] usb 1-3: Product: 802.11n WLAN Adapter
[  125.725785] usb 1-3: Manufacturer: Realtek
[  125.725790] usb 1-3: SerialNumber: 00e04c000001

Hier ist die Lösung beschrieben:

http://askubuntu.com/questions/364972/realtek-8188cus-doesnt-work

First of all, ensure you have the necessary prerequisites:

sudo apt-get install linux-headers-generic build-essential dkms git

Clone the updated driver with git:

git clone https://github.com/pvaret/rtl8192cu-fixes.git

Set it up as a DKMS module:

sudo dkms add ./rtl8192cu-fixes

Build and install the driver, you may need check the version here (e.g. 1.9 may change):

sudo dkms install 8192cu/1.9

Refresh the module list:

sudo depmod -a

Ensure the native (and broken) kernel driver is blacklisted:

sudo cp ./rtl8192cu-fixes/blacklist-native-rtl8192.conf /etc/modprobe.d/

Let’s not take any chances. Instruct Ubuntu to load the new driver when it starts up.

echo 8192cu | sudo tee -a /etc/modules

Reboot.

You’re done.

_{Thanks to P. Varet for this awesome fix.}