After a recent system update, KDE ceased to be able to display Thunderbird's window. Whenever I run thunderbird on KDE, the app appears to run well (it even checks out emails and addons such as firetray even display how many emails have been received) but the applicaiton window doesn't appear anywhere.

This problem doesn't manifest itself when I run Thunderbird on Unity, or Firefox in either desktop environment.

Does anyone have any idea on how to fix this problem?