I ran across this strange problem this morning that I thought I should share with you.
Problem: Sound effects on my Mac have stopped working this morning. First TextExpander stopped making any noises, then I can't play any sounds in System Preferences. What gives?
Solution: Turn on your speakers... Nimrod!
Although this is somewhat embarrassing, the point is very illustrative. Check the most obvious solution first! I worked in tech support for about 4 years. If there is one lesson I learned it is this one. If someone's network has gone done, make sure the cable is plugged in. A machine won't boot? Make sure the power is plugged in. Can't connect to your Wifi router, make sure it is turned on.
This sort of obvious stuff solved about 50% of all the tech support calls I received. So remember, always check the obvious solution first. You will be amazed at how often it is the solution.