http://www.peteducation.com/article....articleid=1406

That article tells a bit about tapeworm and Cestex. Although I confess I've never heard of a case of an animal still passing segments after being given this medication. I suppose it could be from segments already on the stool that are coming out, but maybe call your vet to be sure.

As far as I know tapeworms take 4-6 weeks to show up after ingesting a flea or other carrier of tapeworm (rodent, etc). It's possible they could have ingensted a flea from your neighbors house, or if you had a lag time between Frontline Plus applications, or if they've gotten into garbage or something and got some undercooked meat. Either way the meds your vet gave you should take care of the problem but I would call him/her about still seeing segments just for reassurance.