I have tried this manually and through PlayOnLinux but got the same result.
I installed the latest versions of each under 10.10 and now 11.04 then tried to run steam. I managed to get it going, log in and then it does everything (updates, logs in, brings up main screen) until the news pop-up shows up and this crashes it without any warning.
I'm sure I've read of other people having this problem on the net but also wonder if its my graphics card drivers? I have an old XT1900XT so as far as I know isnt supported by the official ATi drivers. Ubuntu installed the 'Additional Drivers' by default which I presume are the free ones. Could this be the problem? I have however got Guild Wars working (well upto the log in screen, forgot my details ) without any problems.