I just encountered this for the first time yesterday, and was absolutely perplexed by it. So much so, that I completely reversed my commit to walk through it to try and figure it out.
Even though I’ve now found that including one of my services in another service is creating this problem, I did stumble upon this resource from Misko Hevery. Very well done indeed for helping you figure this problem out: http://misko.hevery.com/2008/08/01/circular-dependency-in-constructors-and-dependency-injection/