Lansbury levelled the scores just after half-time, with Forest going in at the interval trailing to Andrew Crofts' header just after the half hour mark.
Two goals in three minutes put Forest in the driving seat, with Lansbury slotting home from the spot almost immediately after Darius Henderson had given them the lead before Nathaniel Chalobah was sent off in the 67th minute as Forest finished the match with 10 men.
Brighton went into the game having scored only four goals in their previous five matches and, in a lively start, former Newcastle winger Kazenga LuaLua provided an immediate threat for the Seagulls.
McGoldrick scored twice inside four first-half minutes - his fourth and fifth of the season - to give Ipswich a 2-0 win and lift them into the Sky Bet Championship's top 10.
Brighton had no answer after McGoldrick's quick-fire brace and seeing a golden chance wasted by midfielder Andrew Crofts with the scores goalless.
Garcia, who was left fuming after referee Stephen Martin waved away second-half appeals for a penalty when Will Buckley's shot hit Tommy Smith's arm, believed McGoldrick was the big difference at Portman Road.
We knew McGoldrick could be a threat and today he showed that he is a player who can play at a higher level. He was the difference between the two sides.
Wanderers had taken a first-half lead after Seagulls winger David Lopez put through his own net, but four second-half minutes saw Brighton score three times to leave Dougie Freedman's men still without a win this season.
Jay Spearing put through his own goal in the 53rd minute, before Inigo Calderon and Will Buckley both found the net to stretch the Amex club's unbeaten run to six matches.
David Ngog failed to keep his cool when one-on-one with keeper Tomasz Kuszczak, who made a save down low to deny the French striker after a mix-up in the Brighton defence.
Martyn Woolford drove the Lions ahead shortly after the break and the visitors had Alan Dunne sent off for two bookable offences before Ulloa struck a minute from time.
Millwall settled quickly and Brighton's Spanish defender Inigo Calderon put a Dunne cross behind for the first corner of the match before a goal-bound header from Woolford was saved by goalkeeper Tomasz Kuszczak.
Brighton's Dutch midfielder Kemy Agustien drove wide from the edge of the area in the 16th minute after the ball was squared to him by Rohan Ince.
The Seagulls went into the game with Argentinian Ulloa as their only fit striker.