I have had quite some problems with my Samsung 900x3a and it’s wireless adapter. For some reason, it showed up the wireless connections fine, but it wouldn’t connect to encrypted networks. Sometimes, if I tried a couple of times, it would suddenly manage to go through. However, I now have a solution which seems better (not perfect, but better) which was mentioned on the Ubuntu help pages : switch off and back on your wireless card !
I had tried everything from uninstalling, re-installing the proprietary driver, downloading a new version, etc. but this simple solution did it in the end…
This helps me get around the problems and everything is working now. Hope this helps someone else out that is having the same problem I was :).
Edit : I just found out another thing that was a problem for me : IPv6 ! For some reason I couldn’t figure out, my laptop would now connect to every network, except for my home wifi (BT Home Hub). By going to Network Manager -> IPv6 Settings and selecting “Ignore”, I have NO MORE WIRELESS PROBLEMS :).