Hi, I am now 90% certain that the reason for my graphics artefacts is down to radeongate / defect discrete gpu. MBP 2011 i7 quad core. (System is running fine when forced to integrated gpu via gfxCardStatus). Reinstalling OS 10.7 didn't help solve the problem either. So unless there was a hidden GPU firmware update that came with OS 10.9: Radeongate. Apple doesn't acknowledge the problem. Many reports of Apple's logic board replacement not solving the problem. So I am thinking about re-balling the gpu. Two questions: 1) How difficult a job is re-balling for a good technician, provided they've got appropriate equipment? I mean: is it more or less a "standard job" for a dedicated laptop technician? (In medical terms: is it like healing a broken leg or is it more like "brain surgery", where doctor's skills are probably more important than the actual equipment?) 2) How many people here have had their gnu re-balled? And how long ago? Would you do it again?