I thought PB Mining had already sunk. I saw a few threads saying they have stopped paying and then a recovery thread admitting that they have to close.
They have been extremely scant on details about their "recovery" although they are claiming to be in the process of trying to repay their investors. One can only speculate what they are doing, however I would guess that it is one of two things:
1 - if they were in fact mining with hardware then they are probably trying to sell off their existing hardware in the secondary market and use those funds to repay customers
2 - if they were running a synthetic operation (eg no actual mining) then they are stalling in an effort to further cover their tracks (logs getting deleted over time ect)