Did anyone mention that it might be the timing belt tensioner yet? I haven't had this issue, but there are a couple of threads around here, somewhere, describing a ticking sound that turned out to be just a bad timing belt tensioner. Only way to check that is to pull the timing belt covers off and check the tension, or lack thereof, of the belt.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless