From the research I've done so far, I believe the problem is originating from a poor manufacturing process for the heads in Malaysia. The Heads are also manufactured in Thailand and Japan. Also, some of the older WL's have a poor quality head gasket that can fail easily.
The forums also mentioned that the manufacturing process was changed in Malaysia along with the gasket material a few years back, so newer engines may not suffer the same faith.
IMPORTANT: These are just some notes I've made from forums based in other parts of the world, in other words it's just "talk" from countries mostly in Asia,
but I haven't gotten any info from an actual manufacturer. Still looking for something concrete.
If all of this is true, you then have to figure out where and when your engine was manufactured

In the mean time, read through this thread to be on the safe side:
http://www.trinituner.com/v3/forums/viewtopic.php?f=41&t=314719&hilit