Have you set your sheet and helix part in your pdb? For my personal case, things you experienced happened when this part wasn't built. I guess that PyMOL cannot find the secondary structures as softwares like Rasmol can. Try to determine your secondary structures with DSSP for example and to paste it in your pdb file before loading it in PyMOL, your cartoonish rendering should be great :)
Cheers Virgile ADAM
