Cannot insert nummeric value of variable assumed real

Hi

I have a problem with an assumed real variable that are not inserted into equations if it is given an nummeric value. I have tried to make and example below:

> restart;
> with(plottools);
> with(linalg);
>with(plots);
> assume(theta, real);

>A := e^(I*theta)

... alot of other stuff

>theta := 0
>A             # here is the problem
                                           e^(I*theta~)

>A:= e^(I*theta)          # but if i define the equation after setting theta = 0 it does what it is told
                                          A := e^(I*0)

If Ido not assume theta real the problem is not there. Does anyone know what the problem is?

Thanks in advance.

regards Brian Bak