I am having a problem with Audacious, which I am told appears to actually be a problem with xfwm4. I first posted a bug on the Audacious bug tracker: http://jira.atheme.org/browse/AUD-256 but was referred here.

The problem is that when the Audacious window is rolled up and then unrolled (implemented via shape masks), xfwm4 doesn't realize the change has been made until focus is first given to another window.

Steps to reproduce:
1. Set the view to use the Winamp Classic Interface. (The skin doesn't seem to matter; I tested multiple skins.)
2. Roll up the main window by double-clicking on the title bar or by using the Ctrl+W keyboard shortcut.
3. Unroll the window.
4. Click anywhere in the window except for the title bar and the click will go "through" the audacious window and to whatever window is under it. 

I am using xfwm4 version 4.6.1 (revision 29817) for Xfce 4.6.1, packaged for xubuntu 10.04 x86_64. I am experiencing this problem with Audacious 2.4-rc2, but also experienced it with the default version (2.3?) that shipped with xubuntu 10.04.