Wow, thanks for the quick replies everyone! I'll try rousting the yeast and bumping the ambient temp a bit (I do not have fermenter temp control yet).
Also, I usually do rack to secondary after a week, and stay in secondary for another week or more, but when I did this with my first 1968 batch, and then bottled on 8oz DME, I ended up with a very flat beer after even 2 weeks in bottles. I'm thinking the high flocculation resulted in no (or very few) yeast in the final bottled beer, so nothing to eat my priming sugar, and thus no carbonation. How do you all manage priming for bottling with 1968? Or are most folks who use 1968 doing force-carbed kegging?
I force-carb now, but I never ran into any issues with 1968 back when I was still bottle-conditioning everything. But 2 weeks is the bare minimum for acceptable carbonation when bottle-priming under even the best conditions. I usually allow 3-4 weeks before I decide that there was an issue.
It could be that since 1968 is so flocculant that there is less yeast in suspension that makes it through to bottling, which in turn may take longer to finish carbonating. but that's just a WAG on my part.