Both sides came into this second league game of the season on the back of getting a point on the opening day.
Palace made one change from their midweek cup tie with Freddie Sears coming in for Victor Moses and Alan Lee starts after coming off the bench to get his goal seven days ago.
The home side enjoyed much of the early possession and won the first corner of the afternoon in the ninth minute from Jamie McAllister which found Jamie McCombe at the far post but his effort was cleared by Paddy McCarthy,
Palace's best chance of the opening quarter fell to Sears after a good exchange of passes from Darren Ambrose and Neil Danns but the strikers efforts from just inside the box was blocked by McAllister. Just minutes later more danger from the visitors as Danns did well on the left hand side and his cross from the line had Goalkeeper Dean Gerken struggling to reach the ball so it was left for Lewin Nyatanga with a clearing header to avert the danger.
The 'keeper did better with a Lee header just past the twenty minute mark when the target man got on the end of a Danny Butterfield cross but Gerken parried the ball away.
Palace's Julian Speroni was the next keeper to be in action as the half hour mark of the game came when he saved a shot low down by Ivan Sproule.
The deadlock then appeared to have been broken but for some reason an effort from Sears was ruled out by Referee Rob Shoebridge. The striker picked up the ball from an Alassane N'Diaye header and put the ball past Gerken and into the net but after consultation between the ref and one of his assistants the goal was not given.
Fury amongst the Palace players and on their bench as there was just not any reason as to why the 'goal' should not have been given and the protests continued as the half time whistle went.
First team coach Keith Curle came on the field as both sides left for the break to keep the Palace players away from the official but you can understand their frustration as they should be ahead after the first forty five.
An early opportunity at the start of the second half for City as they are awarded a free kick on the edge of the box when John Akinde is felled just outside the box. Paul Hartley's effort is blocked by the Palace wall and the ball is cleared.
Two chances at the other end for the visitors at the other end within minutes as Paddy McCarthy headed a Darren Ambrose corner just wide of the post and then an Ambrose free kick went inches wide from a strike just outside the box.
It then became Gary Johnson's side to have a goal disallowed. On 51 minutes a shot by Akinde was parried out by Speroni and the ball fell to Hartley but he was in an offside position when he put the ball into an empty net.
Shaun Derry nearly put his side ahead with a powerful left foot shot from eighteen yards out but Gerken saved well low down as chances were now coming at both ends of the pitch.
Palace's set piece specialist, Ambrose, was given another opportunity to show his skill when N'Diaye was felled and his free kick was deflected just wide of Gerken's left hand post on 72 minutes.
As the game went into the final stages Marvin Elliott saw his header go wide as Speroni came out to collect but he could do nothing about the goal in the 89th minute.
A clearance from McCarthy goes to straight to Nicky Maynard and he makes no mistake as he passes the ball into an empty net as Speroni had come for the ball which the defender cleared.
A late free kick from Derry was saved low down by Gerken at the second attempt as substitute Victor Moses closed in but there was no way back for the disappointed Palace side.
The goal that was not given will be the talking point from this one as Palace travel back to London still unsure as to why the first half effort was ruled out by the referee. A decision which proved so costly following Maynard's late effort which gave the Robins their first win of the new campaign.
Bristol City Gerken, McCombe, Nyatanga, Orr, McAllister,Skuse, Hartley (Fontaine 90), Elliott, Sproule,Clarkson (Akinde 46), Maynard.
Subs Not Used: Basso, Johnson, Williams, Blackman, Brian Wilson.
Crystal Palace Speroni, Butterfield (Lawrence 90), McCarthy,Fonte, Hill, N'Diaye, Derry, Danns, Sears, Lee (Scannell 90),Ambrose (Moses 90).
Subs Not Used: Flahavan, Clyne, Carle, Ertl.
Att: 14,603 Referee: Rob Shoebridge (Derbyshire).