Browser problem with images

[LeleleleMAXIMUM]

All the browsers I've tried on this machine show some images (I'm guessing all pngs) as jpg.

I thought I could work around it by saving the images, but even if it saves them as png, they still get bad jpg artifacts.

It even happens to png images I've uploaded.

Google is no help at all, I've tried different wordings of the problem.
It's driving me nuts on a spriting forum.

Help?

[Ngamer01]

What browsers are you using and what's your OS?