Terrain has "invisible" wall collision.

I created different terrain and on all of them I have the same problem. My character sometimes act as he’s hitting a wall in the middle of nowhere. He can’t move forward anymore. Please, how can I fix that ?
Also I’m a new Unity3D user so maybe the solution is obvious since I haven’t found a post about it…

Tdiddy to the rescue!!!

Ok, so i found another post, referring to this one with no answers. So I started thinking about what I had been doing. My setup is a square terrain, some slopes, and of course some forests for good measure.

Now I had been trying to get the tree painting tool to work but i think it paints fractals based on some of the stuff I was reading. I’m not sure on this, im still in experimental mode. I assumed this was like “Hey Unity, here’s a prefab” and Unity would be like “Ok, ill randomly distribute some of these for you.” But no matter how many times I clicked nothing happens, at least, nothing appears to happen.

Go back to the tree tool and erase those invisible trees!

Swish!