differential equations - Using NDSolve to find particle trajectory

I'm trying to simulate a particle in an electric and magnetic fields, but numerically instead of analytically. This is basically solving the equation

$$q \cdot \left(p'\times B\right) + q\cdot E = m p'',$$

where $p(t)$ is the position in $(x,y,z)$ coordinates.

After viewing a few topics on this site, I've got a good idea on how to get the solution using NDSolve, but my program gets stuck, and doesn't come up with anything.

b = {1, 0, 0};
e = {0, 0, 1};
q = 1;

m = 1;

sol = NDSolve[ {q*e + q*Cross[D[pos[t], t], b] == m D[pos[t], {t, 2}],
     pos[0] == {0, 0, 0}, (D[pos[t], t] /. t -> 0) == {0, 0, 0}}, 
   pos, {t, 0, 1}];
ParametricPlot3D[Evaluate[pos[t] /. sol], {t, 0, 1}];

It is also worth mentioning that if you remove the $q\cdot E$ term, the calculation is finished, but nothing shows up in the plot.

Answer

The main problem is that your pos is not seen as a 3D vector.

The cross product is therefore interpreted as a scalar:

q*Cross[D[pos[t], t], b]

when adding this to the vector q.e this 'scalar' term is added to each of the vector components:

q*e + q*Cross[D[pos[t], t], b]

This won't work, instead do:

b = {1, 0, 0};

e = {0, 0, 1};
q = 1;
m = 1;

Define pos as a 3D vector. Also take more time than a single second:

ClearAll[pos]
pos[t_] = {px[t], py[t], pz[t]};
sol = NDSolve[
  {
   q*e + q*Cross[D[pos[t], t], b] == m D[pos[t], {t, 2}],

   pos[0] == {0, 0, 0},
   (D[pos[t], t] /. t -> 0) == {0, 0, 0}
   }, pos[t], {t, 0, 20}]

ParametricPlot3D[Evaluate[pos[t] /. sol], {t, 0, 20}]