Gnome-shell requires acceleration of to work. For this a nvidia card
with the nvidia-driver, or a Intel/ATI KMS enabled card is needed.
For the nvidia users no other changes are needed. For Intel/ATI KMS
driver the user needs to have read/write permissions on
/dev/dri/cardN (usually N=0). If gnome-shell is launched from gdm, the
gdm user also needs this access.
Access can be granted by adding the user(s) to the video group.
% pw groupmod video -m jerry