It has been discovered that Badass Ranks - which are increased by completing in-game challenges - are being reset, and that Golden Keys are being removed.
While the problem appeared with the release of the 'Mechromancer' DLC earlier this week, developer Gearbox Software said the new content and glitch were unrelated.
"The good news is that the release of 'Mechromancer' and today's update are not connected to the occurrences of Badass Rank being reset," read an official statement.
"While the timing may appear coincidental, it's a separate issue that we are continuing to investigate."
Earlier today a leak suggested that the first expansion would be pirate-themed.
Copyright: 2K GamesThe pack is likely the first of four pieces of DLC releasing between now and June 2013.
Released last month, Borderlands 2 was the biggest-selling launch of the year until the release of FIFA 13.
> Read Digital Spy's Borderlands 2 review
Watch the launch trailer for Borderlands 2 below: