Ok, I've been thinking for some time now that the True Power - drawn from Shai'tan - is very much to the true source what matter is to anti-matter. Sort of. What I'm really getting at is that the True Power can block the true source or disrupt it's flow.

I think the walking dead and the fact that Webs of Saidar are failing, stem from the same source. With the Sha'tan gaining more freedom, is able to cause minor disruptions in the true source. Since in the WOT world, the true source is responsible for everything from Newton's third law, to driving the wheel of time, I don't think it's a big leap to say that the source also serves as the barrier between worlds - between the mirror worlds, TAR, and even the world of the dead. Thus disruptions in the source cause small holes in the barriers. The dead aren't in Randland, as much as to say that the world of the Dead and Randland are the same place in the pockets where the source is disrupted. Why can they walk through walls? Because the disruption isn't complete so from the dead man's perspective the wall doesn't really exist.

Finally, there is an aside theory. Again, it still falls from the idea of disrupting the source, but maybe it's not the dead that people are seeing. Maybe it's people from mirror worlds - people who still are dead in Randland but alive in those mirror worlds. The dead seem as curious about the living as the living are about the dead. Maybe the disruption creates a thinness in the pattern and two mirror worlds intersect. To dead man who frightened Kireyn is really a man in a mirror world, staring at what he believes to be a ghost of Kireyn. He walks through the wall, because in the mirror world, the wall isn't there.