PayPal buttons disappeared

I just upgraded a site from regular WP2.8.3 to WPMU2.8.4. I have PayPal buttons on the site I migrated and they have disppeared. Part of the button code is being stripped off each time I re-save the page.

I figured no big deal, I just need the Additional Tags plugin. It's working fine for other embedding (google map for example) but my PayPal buttons are still MIA.

Any ideas?