Uneven brownie baking? I used to make the best brownies, all the time. They came out perfectly without any effort. Duncan Hines, Hershey's, Betty Crocker-- all out of the box, all simple, all delicious.

But lately (without me making any perceptible change to my strategy) things have taken a turn for the worse.

I bake them for 40+ minutes, they're not done. 8x8 glass tray as always, but the middle is still doughy and moist. Not in the good way, more in the play-doh way. I bake them for 90+ minutes, they're still not done. But the outer edges bake normally, so they end up too crispy to be good, although somehow miraculously not burned. Just the middle is completely underbaked.

Can anyone take a guess at what might cause this?
Your oven temp may be off - check your oven temp.  Get an oven thermometer and check your temp.