Hi Bill,
BS> I don't think this is an error. Upekkha is the attainment
BS> of the third jhana. In the fourth jhana, upekkha is
BS> stilled, so attention to upekkha becomes a hindrance.
Thank you. Indeed I have found a confirmation in Tapussa sutta
http://www.accesstoinsight.org/canon/anguttara/an9-41.html
Metta,
Dimitry