Dummy me!!! I had somehow overlooked the MAC filtering setting in my 2nd base station. It was on and had laptop's MAC address there, but not my N900's MAC address. In router the whole filtering was set off. So I set it off also in my base station. And now it works! :-) Great. Stupid mistake, but luckily I posted the question into this forum so it kind of helped when I did yet another look on the differencies of settings between these two stations.
Thanks!