For all questions, it helps to know what version of NX you're using as well as all the settings in the dialog for whatever command is giving you issues. The more we know, the better we can help you. Pictures speak a thousand words, as well.
Thanks.
Tim Flater
NX Designer
NX 9.0.3.4 Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB