[Wine] Cannot log into Steam

[yuastnav]

Hi,
I just wanted to try Steam using wine and it doesn't work.
I get to the login prompt and it tells me to enter my username and password. I do that but Steam tells me that it failed to login because the account could not be found or the username/password combination is wrong.
However I can actually login on Windows and on the Steam website so the username and password are definitely right.
I'm using wine-1.1.42 under Debian Squeeze (6.0).