DFF is checking against the rules defined in the 'Setup' on the Verify Design dialog (right below the Start button). You may have a clue there.
I don't remember if 'View Report' shows any additional information or not. Try that.
Don't forget that if you zoom out to the entire PCB area you might find more errors because (some of) the error check only checks what is visible on the screen so you don't get overwhelmed. That is a feature of PADS that burns a lot of Newbies.