At the time, the Saints seemed to have taken charge after a nightmare opening quarter of an hour. Grenoble claimed a heel against the head at the first scrum and then won penalties at two of the next three scrums.
Corrihons opened the scoring with a seventh-minute penalty before converting his own try seven minutes later. But Northampton went ahead before the interval through dazzling tries from their wing Ben Cohen and the Wales centre Allan Bateman while Paul Grayson added two penalties to give them an 18-10 lead going into the final quarter.
However, Grenoble recaptured the initiative as Corrihons kicked a penalty and then converted his second try which resulted from a galloping break by Emmanuel Amapakobo.
The 1998 European champions Bath survived an early scare before running in seven tries on the way to a 56-15 Pool B win in Padova. After surrendering last weekend at home to Toulouse due to a late error, Bath handed their Italian opponents a breakaway try after only eight minutes when the Australian wing Brendan Williams intercepted Mark Regan's misdirected pass and cruised home from 45 yards.
Normal service resumed after 15 minutes when Iain Balshaw went over after exploiting an overlap and five minutes later Tokunbo Adebayo scooped up a loose ball to run in from 50 metres. These touchdowns opened the floodgates and further tries followed for Balshaw, Chris Horsman, Steve Borthwick, Angus Gardiner and Andy Long while Jon Callard kicked five conversions and three penalties. Jon Preston slotted Bath's other conversion while Hector de Marco supplied a conversion and a penalty for Padova with Williams crossing for his second try late in the game.
Colomiers' Richard Nones has been banned for two years for eye gouging following his injury-time dismissal in Friday night's 22-14 defeat at Pontypridd in Pool D. The 30-year-old loose-head prop was sent off after the touch judge, Bertie Craig, spotted his assault on the Pontypridd tight- head Sven Cronk during the game's final scrum. The Welsh Rugby Union delegate Huw Lewis, acting as the match commissioner, handed down the 24-month penalty after a lengthy post-match disciplinary hearing.
Steaua Bucharest restored Romanian pride after a disastrous World Cup with a 30-20 European Shield success over Connacht, but Dunvant lost 42-16 at home to Narbonne.
Worcester remain top of Allied Dunbar Premiership Two on points difference despite losing their 100 per cent record with a 20-9 defeat at second- placed Leeds. Rotherham and Exeter are third and fourth, two points behind, after victories over Moseley and London Welsh. Jewson League One leaders Otley surrendered 17-9 at home to Wharfedale but they are still two points clear despite Rosslyn Park's 46-8 romp at Blackheath.