How to use TP-Link Tl-wn821n v2 with xubuntu 12.04

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http://askubuntu.com – I just changed from opensuse 11.2 to xubuntu 12.04, installation via Live-CD. The computer is connected only via usb wlan to the www. If I start iwlist wlan0 scan as sudo there is a long, long list...it seem's to work but. There is no connection possible. How can I solve the problem? (HowTos)