Well, I noticed the AI mainly gets FUBARred (I love that word

) when it is either:
1. Trying to build two things at the same time. It can't figure out which to build first to it ends up getting stuck. You need to set a prerequisite for the triggers so that it will only build one of the buildings when the other is finished.
2. Trying to build something it can't build. This means that when you execute a script that tells the AI to build something it can't build (yet), it gets stuck.
The AI will build something though if it is capable of building but all of its dozers are occupied. In that case it sometimes builds an extra dozer (not sure on this). This happened to me once too:
http://www.deezire.net/modules.php?n...ewtopic&t=4616.