Possible map problems:
- try a fresh mxd
- try deleting Normal.mxt
Possible data problems:
- try exporting feature classes to fresh FGDB or shapefile - are these GDB feature classes, shapefiles, or other?
- are the feature classes participating in a network or otherwise doing something non-standard?
- does this type of lag occur with other feature classes?
- do the feature classes reside on your machine?
Basically, as you've described them, the feature classes sound pretty standard so I suspect there is something more systematic going on. At the very least, you should be able to start a new mxd, add one of the feature classes, and edit it with no problem.