Some moms have been told by pediatricians that they must wean their babies at 6 months, otherwise they'll have to take "remedial swallowing classes". This appears to be utter nonsense.
Solid food: The AAP says breastmilk exclusively for 6 months, then introduce solid foods (http://www.aap.org/advocacy/wwestand.htm). So that's the establishment view. On the other hand, their web site doesn't have a single reference to "swallowing classes", and I can't find any such thing searching on the wider web either. So if you want to be an informed health consumer (i.e. pain in the butt) you might ask for a reference for why she thinks such a thing. Don't get put off with "it's in the literature" or "you wouldn't understand". Any doctor who won't explain is better off without patients.
The technical term for "difficulty in swallowing" is dysphagia, and in fact there's a whole web site at http://www.dysphagia.com devoted to it. I prowled around in their mailing list archives, and I don't see any swallowing classes their either. Or any reference to a correlation between dysphagia and late feeding of solid food. They have a small chunk of their site devoted to infant feeding, but the only things they seem worried about are cerebral palsy and fetal alcohol syndrome.
Of course, this is all negative evidence. Maybe there is a good study somewhere that shows difficulty in swallowing for infants who start with solid foods later. But if there is, I can't find it online.