Script Tags being removed from Text Widget

I am trying to add a google adsense type script (actually, ClickBankPro) to a "text" widget in multisite (Pro Sites). It works okay for the MAIN SITE (logged in as superadmin) but when I log into any subsite as a normal admin and try to add the script to the Text Widget, the "<script>" tags etc are deleted when I press save. Using different themes seems to make no difference - I have also tried the "Enhanced Text" plugin.

After hours of mucking around, I thought it was time to ask for help. Can anyone point me in the right direction?