System Image Utility App. 10.5.7 does not recognize any 10.6 disc...

i hope someone can help with this, i have not found anything related yet.

i am trying to create an netinstall image from any (upgrade, box set) 10.6 DVD and it is not being recognized by System Image Utility App. 10.5.7

the 10.6 DVDs mount fine on the desktop and in the finder.

the 10.6 DVDs do not show up in the left hand pane. according the System Imaging_and_SW_Update_Adminv10.5.pdf I should see them there but they never show up.

is there something i am doing wrong? i have successfully created a netinstall image with a 10.5 DVD using the same software.

thanks in advance.