Sounds like somehow along the process the 8th bank gets deselected. If you press Shift, the 8th pad should be the one to light up (red, I think). Make sure that Bank 8 is selected when trying to use the pads for clip control. If you are sure that it's selected, then it might be that the script somehow got corrupted, but I never heard of it happening.
Keep in mind that if you select another bank, Live mode will be deactivated (if you press Shift and any pad 1-7 light up, then Live mode is disabled). Also, with every opening of Ableton, you'll have to manually select your 8th bank on the controller( it's what I remember, might be wrong) so always check if something goes wrong.
Hope this helps.