Attached Link: http://www.philc.net/tutorial2.htm

It may be because you did not weld the vertices. There is an option in the grouping tool window. I'd need to see the actual model to be more accurate. If you feel that would be helpful then by all means send it to me and we can work through it.

If you are at the stage I think you are you may find the tutorial on my site of interest. It certainly contains all the information you are looking for with several worked examples. Please note however that there are loads of other tutorials available besides my one. Most are free. Best judge of how good they are is to see the work the writer is accomplishing.