http://bugs.winehq.org/show_bug.cgi?id=23353
--- Comment #10 from Brandon Howard FinalCrisisSX@Hotmail.com 2010-07-02 22:57:49 --- My apologies one last time. It seems most of those things weren't even necessary to reproduce this.
Simply..
1) Right click the system tray icon for steam, and click "Library". 2) Right click the system tray icon for steam again, and click "Friends". 3) Try to click the close button on the steam Friends window. It will not work. It will act like it's going to close (start fading out), then pop back up.
Note: The order seems semi-important. I don't know why, but it apparently doesn't work AS consistently switching 1 & 2.