Albion were condemned to their third defeat in six games by a controversial penalty.
Referee Paul Rejer penalised teenager Adam Hinshelwood for handball.
Danny Higginbotham scored from the spot in the 29th minute to avenge Derby's defeat by the same score at Withdean a month ago.
It was most unfortunate for Hinshelwood, called up in place of the banned Paul Watson.
He was running back towards his own goal and being challenged by Lee Morris when Rejer ruled he had handled as he fell.
Steve Coppell's Seagulls produced another Jekyll and Hyde display in front of a rain soaked crowd of 25,786 at Pride Park.
Michel Kuipers kept them in touch in a disappointing first half with a series of fine stops.
The big Dutchman saved shots from the influential Craig Burley (twice) and Warren Barton.
Kuipers also made a fantastic one-handed deflection at full stretch from Chris Riggott's header from a Burley free-kick.
Albion looked a totally different team in the second half once Coppell switched to 4-4-2 and brought on Paul Brooker for Nathan Jones, then Gary Hart in place of Richard Carpenter.
They carried much more of a threat, Bobby Zamora almost equalising with an angled drive which was diverted for a corner by England Under 20 keeper Lee Grant.
Albion are still next to bottom after Sheffield Wednesday lost 2-0 at home to Gillingham.
Eleswhere at the foot of the table Stoke held leaders Portsmouth to a 1-1 draw at the Britannia Stadium, Grimsby were beaten 3-0 at Preston and Bradford eased their worries with a 1-0 home win against Nottingham Forest.
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