solaris.xpm became solaris.xpm.gz. However, that alone shouldn't cause a hang - though it may appear so if there were other problems starting the graphics window (if the drivers don't work properly, the error message telling you GRUB couldn't find the file "solaris.xpm" will be hidden behind a black graphics window.)
You should only need modify the menu.lst entry to specify solaris.xpm.gz rather than solaris.xpm. Either way, you definitely shouldn't be getting "stuck." -- This message posted from opensolaris.org
