I got Tk spinboxes to work via a kludge. I stole a copy of tcl 8.4 and tk 8.4 from Python 2.4 and laid them onto Ruby 1.8.2.
add the tcl8.4 folder and tk8.4 folders from python into the ruby lib folder (you can leave the original tcl 8.3 and tk 8.3 alone)
put a copy of the tcl84.dll and tk84.dll from python into the ruby bin folder.
rename your old copies of tcl83.dll and tk83.dll just in case
rename the new tcl84.dll and tk84.dll to 83 and now tk 8.4 works with ruby