I too had this problem. I had been developing my vi over several days with no problem connecting a control to the timed loop dt terminal. Then, I got an error saying that the node was not executable. I tried control ^ b and the error disappeared and now runs fine again. Anyone know what control ^ b does?
Ctrl+b removes all "broken" wires on the block diagram. That's why I made the comment earlier in this thread about the timed loop terminal wiring mechanism being suspect.