Problem solved. Had to back everything up and reinstall Opera clean. But it worked.

@sgunhouse Thank you for your reply. Could you please be more specific?

@donq. Yes, I have. It has no effect. (But thank you for the suggestion.)

I've just started having a weird problem with DevTools. As seen in the image, everything is gigantic -- and DevTools is unusable.

I've got the latest update of Opera installed and have tried with all extensions disabled after restarting.

Is there anything I can do? Or is this a new bug that Opera must attend to?