Solving simple PDE Error

I'm trying to solve a transient diffusion equation:

dC/dt=D*d/dx(dC/dx)

Initial condition: C=0 x>0

Boundary conditions: C=0.3 at x=0 dC/dx=0 at x=1

Is it possible to use pdepe to solve? I keep getting error: "This DAE appears to be of index greater than 1."

[Tom]

Can you post your boundary function?