http://bugs.winehq.org/show_bug.cgi?id=15263
--- Comment #7 from Sam skipsey aoanla@yahoo.com 2008-10-05 06:51:17 --- Downgrading to various older versions of Wine doesn't fix this problem.
I suspect, from the fact that entries into the AppDB for 1.1.3 before September which test Buying Games say that it works, and those after say that it is broken, that this is due to one of the two Steam client updates in early September, both of which seem to have included changes to Steam's UI.