Mine shows the same as yours, that the module already exists. What does your's show with the command "ps |grep nfsd"?
Here's what my /etc/exports looks like:
/volume1/Movies 192.168.0.*(rw,async,no_wdelay,root_squash,insecure_locks,anonuid=1024,anongid=100)
/volume2/tv 192.168.0.*(rw,async,no_wdelay,root_squash,insecure_locks,anonuid=1024,anongid=100)
/volume4/Music 192.168.0.*(rw,async,no_wdelay,root_squash,insecure_locks,anonuid=1024,anongid=100)
/volume4/Photos 192.168.0.*(rw,async,no_wdelay,root_squash,insecure_locks,anonuid=1024,anongid=100)
/volume3/Movies\0402 192.168.0.*(rw,async,no_wdelay,root_squash,insecure_locks,anonuid=1024,anongid=100)
/volume3/TV\0402 192.168.0.*(rw,async,no_wdelay,root_squash,insecure_locks,anonuid=1024,anongid=100)