For reasons unknown carriages no longer function for me, with any of my saves or characters. I'm wasn't over-encumbered and I've tried turning off my mods in groups, and in total. Nothing seems to work, the drivers don't take the money, and sitting in the back does nothing.

This is extremely crippling for my "no fast travel" character.

I've seen on the forums that there is a new dialogue bug introduced with 1.7, and I wonder if that could be the cause...

did you happen to use the Scenic Carriage mod that allows you to ride the carriage to locations in game time allowing you to watch the trip or jump off when you wanted? If so I believe you need to turn it off a specific way before just deactivating it on your NMM. You have to tell the carriage driver you want vanilla carriages or something to that effect.