invalid entries found

I keep having the "invalid entries found" error in all my apps. These were apps that were working previously (how far back I'm not sure), but I tried to see if it was an error in my coding, and could not find anything. Next, I tried to create a simple application with one single field, and I still had the same error. Is this a known issue, or is it just something exclusive to me?

I do not have "Required field" or "No duplicate entries" checked.