Players seem to have uncovered a bug in Borderlands 2?s Badass Rank system, which sees progress wiped.
All versions of the game seem to be affected, wiping all of your Badass Rank progress and locking you out from any challenges you may have already completed. At the moment it only seems to be affects a small number of players, but be warned.
Thankfully, developer Gearbox Software has acknowledged that there is a problem and is currently working on a fix.
Hopefully the fix will arrive soon.