"How technical" could manifest in different forms. Based on my experience in project management and development management, a project manager must be technical in the sense of competent in problem solving in the domain of the project. It usually requires past experience of development in the related domains, for example, for software/hardware development, such problem solving skills could come from being a senior architect, senior software/hardware engineer, etc. The key is not the detailed knowledge of particular subject, but the maturity acquired from having solved complex enough problem before.
In another sense, being technical could mean more on the meta level, a good project manager should be an explorer, and researcher to abstract out of chaos of unknown to define the right problems for the team to solve. By this definition, such good project manager may not be expert in the domain, but expert in problem solving in unknown domains, expert in defining the right problems for the other experts to solve. In this regard, I witnessed many math major could do very well as project manager.
Sometimes, a good project manager can take advantage of being not too technical in a particular aspect to see the big picture, and earn the excuse to ask "stupid" questions that the experts overlook, or are afraid to ask.
So in conclusion, project manager got to be very technical in project management! I see the danger of some project managers behave as a secretary, or administration assistant.