The browser cache function is causing image upload error (Http error/503 error). Many have suggested workarounds like increasing php mem limit or writing some lines in .htaccess or even changing the image from png to jpg.
None of those worked, and I know caching is a tricky thing to use, so i went and disabled the browser cache while leaving the page cache on, and bam! It uploads without problem.
What i don't understand is, i am logged in as admin, and by default it SHOULD behave like a un-cached website, but alas it just doesn't.
