Harry, that depends on the company you buy from.. probably those Kemco MC's are good quality, but as for any others I have seen, those 3rd party MC's are really worthless. I guess it's just a matter of knowing whom should you buy from. (I'm repeating myself
)
Actually that corrupted data appeared as well in my PS 2 MC.... but those were actually several photos I took in MGS 2. When I erased those cubes, my photos were erased as well.... I took more photos, and more cubes appeared again
I guess that in that case they were not corrupted data, but the PS2 recognized them as such.