I guess it doesn't have a modded bios:

Does it?
With 21 Mhs +++ after Compute mode, seem like your card running at stock bios. For make sure, use AB and set it to a default setting then take the pic, post here.
Error 43, most caused by a driver issue. Yes, you can try to patch the driver (even when you are running on stock bios). Or, load different driver (I suggesting blockchain version) for manually updating your 580 (4GB).
Yes, Im using stock bios on each of my graphics cards, I have not moddifyed any of them.
When you say "For make sure use AB and set it to default setting" what do you mean? What does "AB" mean?
where can I find the right blockchain version drivers for my XFX 580?
Thank you in advance
jillscarbrough