This was helpful. I'm going through the exact same experience, 2.5 L starter at 1.038 OG on a stir plate ~72 F. After 10 hours, no visible activity, no change in OG. I'm going to delay brewing the a day or two.
It might be "ropiness": http://www.byo.com/stories/wizard/article/section/121-mr-wizard/1269-preventing-beer-slime-a-reducing-tannins-but-not-flavor-mr-wizard