imgname= image.split(".")[0..-2].join(".") ### removes .jpg etc from end

Maybe he is using weird filenames that aren't properly handled by this code. (eg. "my.texture.jpeg")

Can you post the names of the files you are trying to import?

#This script was created by Adam Beazley for public use and may be edited.
#http://www.abeazleydesign.com
#Directions
#Just click in the Import Materials button in the plugins menu and type in the location of all of you image files.
#This script will create a material and name it the same name as the image file and then use that file as the texture.
#all textures will come in at a standard scale and must be edited later
#after all materials and textures have been imported into the model, simply add them to your library
#you can then save the library as a .skm library file through sketchup.
#have fun!!!
#
### v1.1 TIG tweaks 29/12/05 ###
#-----------------------------------------------------------------------------
require 'sketchup.rb'
#-----------------------------------------------------------------------------
def materialimporter
   model= Sketchup.active_model
   materials= model.materials
   model.start_operation ("Import Materials") ###undo - see commit at end
   pwd= Dir.getwd.split("/").join("\\")+"\\" ### fix for SU
   dry= UI.openpanel "To Pick this Directory; Pick Any Image File + OK...", pwd , "*.???"
   ### for jpg or png
   return nil if not dry
   dry= File.dirname(dry)
   return nil if not dry
   cwd= Dir.chdir(dry)
   images= Dir["*.{jpg,png,tif,bmp,gif,tga,epx}"]### for all supported image file types
   for image in images
      imgname= image.split(".")[0..-2].join(".") ### removes .jpg etc from end
      mat= materials.add imgname
      mat.texture= image
   end#for image###
   model.commit_operation ###undo all if needed
end#def###
if(not file_loaded?("massmaterialimporter.rb"))
    menu=UI.menu("Plugins")
    menu.add_separator
    menu.add_item("Import Materials") { materialimporter }
end
#-----------------------------------------------------------------------------
file_loaded("massmaterialimporter.rb")
#

Works fine for me ?