A late double from Vicente saw Portsmouth's first visit to the Amex Stadium end in a 2-0 defeat which keeps them bottom of the Championship table.
It was another lacklustre performance that saw Pompey beaten by a side that didn't play too well in honesty, and that will be a major worry as chances remain at a premium for Michael Appleton's men.
Despite this, there have been worse showings this season and the visitors grew into the game after a slow start.
However, Pompey were mainly reduced to long range efforts as Luke Varney came close to finding the corner with his curling effort and Scott Allan attempted to lob Peter Brezevan after the Brighton keeper came off his line.
Varney produced Pompey's only meaningful effort "on target" soon after with Brezovan forced to push the ball out for a corner, but the shot may have been going wide anyway.
All of that effort may have been undone in the last minute of the first half as a free kick sparked a frantic goalmouth scramble which ended with Jason Pearce blasting the ball away.
The second half saw the hosts take control of the game but not before Marko Futacs was bundled over by Adam El-Abd in the box and Pompey should have been awarded a penalty.
They weren't, and 15 minutes from time the players and fans had even more reason to be angry as Vicente went down easily under a challenge to win a soft free kick on the edge of the box.
The ex-Valencia player then struck the ball across goal and into the far corner of Jamie Ashdown's net to give Gus Poyet's men the lead.
Michael Appleton reacted by giving Chris Maguire his debut and by sending Dave Kitson on but it was too little, too late and the Seagulls rubbed salt into the wounds as Vicente scored in the last minute of stoppage time after Kazenga LuaLua handled the ball before passing it to him.
That goal marked the end of another flat Pompey performance which has now become predictable fare under Michael Appleton. Plenty of endeavour but no urgency or quality in the final third.
I have plenty of sympathy for him as he tries to steer this wreck of a football club to safety on the pitch but I think his philosophy will need to change on Saturday.
Nottingham Forest's win over Millwall means that Portsmouth are now eight points adrift of safety going into a crucial run of fixtures, starting with a home game against fellow strugglers Bristol City.
The fact that we have only scored one goal from open play in seven games speaks volumes. Perhaps it's time to ditch the "safety first" approach and just go for it next week?
Pompey Player Ratings
Jamie Ashdown: 6 - Solid return to the side.
Tal Ben-Haim: 6 - Did OK.
Jason Pearce: 7 - A few crucial interventions.
Ricardo Rocha: 7 - Hopefully isn't the next one out the door.
Greg Halford: 5 - Struggled to contain Brighton's wingers at times.
Joel Ward: 6 - Worked hard.
George Thorne: 6 - Did a job.
Scott Allan: 6 - Our brightest player again.
David Norris: 5 - Wasn't really noticed.
Luke Varney: 6 - Pompey's biggest threat.
Marko Futacs: 5 - Wasn't really in it, apart from penalty appeal.
Substitutes
Aaron Mokoena
Adam Webster
Kelvin Etuhu
Chris Maguire (Futacs 79): N/A - Not enough time to see what he could do.
Dave Kitson (Norris 85): N/A - Change was made far too late.