@ChrisUnderwood, I had this problem Friday and again yesterday when I first started working in the project. After making the post, it seemed to go away. And it's working fine again this morning.
To answer at least some of your questions, the three layers I am working with are all shapefiles. Two sit on a shared server, the other on my local machine. I have all three attribute tables open, but I am only editing in one of the three. The editing consists of copying data from two of the layers and pasting it into the third.
I'll post again if the issue reappears, but right now, I'll blame it on gremlins.
