According to their sources, B&N's supply chain partners (who have been assembling the component in Taiwan) have been seeing a higher than expected failure rate on the new screen. It sounds like B&N may have rushed the new device into production before they worked all the bugs out.
I don't usually put any weight in Digitimes' rumors, but this one looks to have some corroborating evidence. The Nook Glow is currently out of stock at B&N, and they've been having a supply issue for a couple weeks now. "Issue" might actually be an understatement; I've heard from several different people that they had a lot of trouble getting one (now I regret having killed mine). I couldn't even get a replacement when I took mine back; the 4 units on hand were all spoken for.
But I'm not so sure that Digitimes is correct in their explanation for the shortage; I've gotten hints that there might be a solution in the works for the fragility issue. And to be honest, I think it more likely that B&N's only supply issue with the Nook Glow is that they can't make them fast enough.
In any case, we're going to have to wait and see.
image by z287marc