Here might feel like a bug :
When you enter windows manager, the whole buttons are in the hidden bar. the active one is remaining empty.
When you try to move any of them, xfwm4 crashes.
Hope this help !
That code hasn't changed, so if there is a crash, it's most likely a regression being introduced bu other changes, possibly by other libs.
Would you have a backtrace? I am not running/using xfce 4.8
*** This bug has been marked as a duplicate of bug 6824 ***