My Dell Latitude D400 with Lubuntu 12.04 can find my wifi network... but can't authenticate the access. What could I check?

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http://askubuntu.com – guys! Well, it's almost unnecessary to mention that I'm an absolute beginner as an [L]Ubuntu user. The fact is my laptop can find any wifi network, but when I insert the password (which is absolutely right, I assure) it asks again for the password few seconds later and it keeps asking and asking and asking... BTW I'm using this same laptop now, but with an wired network I have another computer, a desktop, with Ubuntu using the same wifi network. I've already tried to restart my router and any device. What else could I check? This is what I have here: 01:03.0 Network controller: Intel Co (HowTos)