Algeria goalkeeper Farouzi Chaouchi's error 11 minutes from time handed Slovenia a crucial victory in their Group C match at Polokwane.
Less than 24 hours after England's Robert Green had let Clint Dempsey's shot slip from his grasp in the 1-1 draw in the group's opening game, Chaouchi produced a similar howler.
Slovenia captain and former West Brom midfielder Robert Koren's 25-yard shot was not particularly venomous but the Algeria goalkeeper allowed it to bounce up off his shoulder and into the net.
Only moments before that the Africans had been reduced to 10 men when substitute Abdelkader Ghezzal's needless handball resulted in a second yellow card.
The win puts Slovenia top of the fledgling table and with a chance of qualifying for the knockout stages, an unlikely scenario before the tournament kicked off.
On this evidence it would seem unlikely either nation will cause Group C's 'big two' any problems but, as has so often been the case in the past, England have an unwelcome habit of stumbling over hard-working and resolute teams.
And both Algeria and Slovenia reached the World Cup with play-off victories over Egypt and Russia, countries supposedly superior to them.
Portsmouth defender Nadir Belhadj presented an early threat when he forced Slovenia goalkeeper Samir Handanovic to tip over a third-minute curling free-kick from the edge of the penalty area.
It was a rare moment of quality in a half littered with errors as both sides needlessly gave the ball away.
Valter Birsa's inswinging free-kick from the right touchline forced Chaouchi to punch clear Slovenia's first real chance in the 21st minute.
Algeria striker Rafik Djebbour was lucky to escape punishment after appearing to deliberately catch centre-back Marko Suler in the face with his shoulder on the half-hour.
But Aleksandar Radosavljevic was booked by referee Carlos Batres for barging over Belhadj as he attempted to break down the left.
The resulting free-kick signalled a few minutes of sustained pressure which ended with centre-back Rafik Halliche heading wide Algeria's best opportunity from Karim Ziani's corner.
Just before the interval Karim Matmour's left-foot half-volley flew narrowly over the crossbar at one end while Chaouchi had to acrobatically tip over Birsa's long-range effort at the other.
Both teams changed their strikers early in the second half; Slovenia sending on Zlatan Ljubijankic for the ineffective Zlatko Dedic and Algeria replacing Djebbour with Ghezzal.
But Belhadj's delivery remained the most likely weapon to create the breakthrough as Halliche had a free-kick snatched off his forehead by Handanovic.
Rangers centre-back Madjid Bougherra produced a perfectly-timed tackle to deny Milivoje Novakovic just as he was about to shoot 12 yards out.
Algeria's chances of victory diminished considerably in the 73rd minute when Ghezzal, having been booked with seconds of coming on for pulling Suler's shirt, received a second caution for handballing a long punt forward.
Six minutes later Slovenia captain Robert Koren punished the north Africans with a little help from Chaouchi.
The watching Zinedine Zidane, born in France to Algerian parents and considered a hero in the north African country, was not impressed.
Algeria Chaouchi, Bougherra, Yahia, Halliche, Belhadj,Kadir (Guedioura 82), Lacen, Ziani, Yebda,Djebbour (Ghezzal 58), Matmour (Saifi 80).
Subs Not Used: Gaouaoui, Mansouri, Boudebouz, Bellaid,
Laifaoui, Medjani, Mesbah, Abdoun, M'Bohli.
Sent Off: Ghezzal (73).
Booked: Ghezzal, Yebda.
Slovenia Samir Handanovic, Brecko, Suler, Cesar, Jokic, Kirm,Koren, Radosavljevic (Komac 87), Birsa (Pecnik 84), Novakovic,Dedic (Ljubijankic 52).
Subs Not Used: Jasmin Handanovic, Dzinic, Ilic, Krhin,
Filekovic, Stevanovic, Mavric, Matavz, Seliga.
Booked: Radosavljevic, Komac.
Goals: Koren 79.
Ref: Carlos Batres (Guatemala).