I long ago set the CRS for a linguistic geography project I'm working on involving Oklahoma data (EPSG:2836 - NAD83(HARN) / Oklahoma North), and I have been closely monitoring that the polygon shapefiles I have been creating are set to the same. I've been working on the project for several days now, and all seemed fine today when I started working. But after hours of work this evening, I saved my project again only to discover that all of the polygons that I made before today have now moved hundreds of miles away to the southwest (while still maintaining their relative locations with respect to one another) and shrunk to ridiculously small size. For instance, a nearly 220 km wide polygon originally in northeastern Oklahoma is NOW ONLY 3 METERS WIDE and located in Southeastern New Mexico! All of the shifted polygons still have the same CRS settings as the others, have same relative position with respect to one another, and their attribute tables are intact. I reiterate that every polygon I've made so far in this project is its own separate shapefile, most of which overlap with one or more others. Oh, yes, I freely admit that I'm very new to QGIS, and GIS in general, only having started to teach myself the basics this summer. But I would GREATLY appreciate figuring out what I did wrong and how can I fix it (beyond just scrapping those polygons and starting over again). I don't know of anyone else that uses the program, so there's no one I can turn to.