This issue seems to have just cropped up as of the last patch:
When playing WoW my windows task bar is permanently visible while playing the game. I tried switching the System->Graphics->Display Mode to Windowed and back to Full Screen. But the problem still persists.
As an interim fix, I have my Windows task bar auto-hiding, but any time I go too low on my screen to click a button the task bar pops up again to interrupt game play.
How can I fix this?