Sometimes when switching from a low-res resource to a high-res resource (64x or higher), the text will just look like [][][][][][][] [][][] [][][][][] or something. But when I switch back to a resource that is 32x or below, it gets fixed, but the bug won't go away until a game restart.
I've also noticed that certain materials don't show up as re-textured, specifically for Misa's Realistic 64x pack. The top of birch logs and melon plants show up as default. Then nether brick fences used to show up as white with black dots, but now they're really really dark gray with some blacker dots on it. They should be red – they've been red in the past.