Dripping walls- what's going on here?

Up until now, I have been a firm supporter of Benjamin Moore's new Aura paint line. I used this high-end paint product for virtually every room in our house. But look what has happened to my newly painted bathroom walls!
Ick, right? Those streaks, evidently caused by moisture build-up from the shower, are permanent. They look wet, but they are actually dry, shiny streaks. We don't have a ventilation system in the bathroom, so always leave the window open to air out the room. We also shower with the door open, which you would think would cut down on the moisture.
When we first painted the bathroom, I used a semi-gloss finish, knowing that moisture can wreck havoc on painted surfaces. But the walls are so uneven and full of imperfections that the shine caught every bump, crack and ridge, drawing way too much attention to the flaws. So I repainted it in a matte finish. But these streaks are awful.

Have any of you ever experienced this before? Help, what should we do!