i had the same problem with other tuts around the net, that's why i made mine.. after talking to everyone else at the time it was done, i found that many of them had the same problems and resolved their issues by having the hacked bios on bank 2.. gave it a shot myself and everything worked perfectly.
couldn't tell ya why some chips work better than others, as i'm not the one who builds them.. i can only point you to a way that is known to work for all of the x2.6 chips.. those with the issue, and those without
and yes, the bios you have is a hacked one.. there are only three bios files that aren't (stock, flashbios, and cromwell)