Problems to link to my Wifi Router

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http://askubuntu.com – I have Ubuntu 11.04 and I would want to uptate it. However, my ubuntu does not link to my router wireless. At the end of try it asks me for a password and says "password wrong" I tried to remove the password from the router with free access, but nothing changed. The same pc with Windows links perfectly without problems, same as my cell phone and pc of my wife. The router is TP-link TD-W8951ND, the wireless pen is Tenda W541U I also tried to update the drivers from the Wifi-Pen I tried to install MadWifi Any Idea that could help me? Thanks (HowTos)