The City on this DC form is coming from your federal W-2 (or sometimes 1099). Sometimes the federal form allows a longer name than the DC form does.
The solution is two-fold:
1. go to the W-2 and shorten the city name (from the end) by a few letters, then try to review the state (DC) again. So long as the beginning of the city name is the same and your SSN is the same, this will have no negative effects.
2. If #1 does not solve the problem even when the city has been shortened to just a few characters AND if you imported the W-2, write down everything on the W-2 (or print it), delete the W-2, and re-enter it manually. The import process sometimes adds spurious data that you may not be able to see but which is there.
