At first I only needed something to remind me where the quest givers were, so that I don't run around and look for them for days... :) I used the same code to do the notes for Vendors and Trainers. I'm going to start to add more information to all 3 modules soon, eg. trainers will have info about what kind of trainer, the same with vendors.
This is a work in progress, and with all the suggestions that I've already received it's going to keep me busy for a while to come it seems... :)
I've added Cartographer_Notes as an optional dependency. Please have a look if it solves your problem. I can't reproduce the error tho. On my system Cartographer, Cartographer_Trainers and Cartographer_Vendors are installed in my main wow installation as well as on PTR and everything still works. Are you using the LOD version of Cartographer?
Please let me know if you are still having problems.
Thanks for the quick update Kodewulf - I download your changed _Trainers and _Vendors, both working fine again. In addition to the trainers/vendors I personally add, it also shows dozens I've never been to ... I'm assuming this is from the Notes dependency, and I can live with the busy maps. :)
I didn't know there was more than one version of Cartographer - I always use the one from 'files.wowace.com', not sure if it's LOD or not.