Ubuntu – edimax EW-7811Un USB wireless – sees network but fails to connect to it

Yesterday I got my first Ubuntu (11.10 32 bit) installation (wish me luck), and I ran into a problem with my USB network card.

I use a wireless USB stick by edimax (it is called IEEE802.11b/g/n nano USB adapter or also EW-7811Un).

My problem is that Ubuntu seems to be able to use the USB to see the networks around me, but when I try to connect to my network – it just keeps trying and failing.

I am connected to the internet through a

300M Wireless N Router Model No. TL-WR841N / TL-WR841ND

I have other computers in the house which are able to connect to the internet. And the same computer previously had Windows on it – and it managed to connect to the internet with no problem.

Can you please advise on how this can be resolved?
(what output should I send you?)

Thanks!