Terrain Textures suddenly extremely muddy

So, I've been working on my game for a long time now, back when Unity 3.3 was out. I have since upgraded to 3.4, and again to 3.5. Anyway, I'm working with a 2000x2000 terrain model, 513 heightmap resolution, the Terrain Toolkit addon, and three 1024x1024px textures. Now, everything was working swell for a long time now, but recently I decided to add some trees to my game. I created a tree, which made one below the terrain. No big deal, I was going to make it a prefab anyway. But after I made the tree and went to mass-place it, I noticed that my once moderately detailed textures now look like a single flat color (the only shading is due to the sun.)

What happened? Is there any way I can fix this? It looks the same when I export the project too.

I may only have a lousy intel graphics chipset from 2005 since my video card died, but it hasn't been like this before. My other specs are Windows Vista Home Premium 32 bit, 4gb DDR2 Memory, and a Pentium D processor @ 3.2ghz.