Both sides had gone into the game desperate for a win - United having not won a league game at home for 2 months and their Essex visitors with only 1 win in 12 league starts - so it was somewhat predictable that this encounter should end in stalemate.
The Ducks took the lead in the 7th minute when Naseem Bashir threaded a through ball to John Caesar who planted his shot past Grays keeper Andy Marsh into the corner for his 9th of the season.
The visitors equalised in the 60th minute when Jason Walker was brought down in the box by United keeper Gary Phillips for a clear penalty which Barry Robert converted.
The hosts went back in front in the 80th minute when Mark Risley pushed Michael Danzey in the box and Gary Cobb fired home the resulting penalty before United suffered a double blow.
First, in the 80th minute when defender Steve Smart was sent off for a late, ill-advised and senseless lunge at Grays sub Peter Hickles.
Then 3 minutes later Smart's indiscretion effectively cost his side all 3 points when Robert ran unchallenged for half the length of the field down the right (an area guarded by Smart) before crossing for John Ray to hook home the equaliser.