That's very strange. I just tried it again - the very first "Hello"-box example. No problem.
Step 1) Put this in a file called hello.pic
Step 2) Run this line:
pic hello.pic | groff > hello.ps
Note that the picture is small - at the very top of the page. Since gv will center the displayed page, you may have to scroll to view the box. (Or try a different viewer, eg. display from ImageMagick.)