Opacity on hover not working in Chrome or IE

Urg! I'm using a WordPress plugin to create boxes with an opacity effect upon hover but it doesn't seem to work on Chrome or IE and instead they fades to opacity: 1 (100%) although I have modified the CSS to opacity: 0.2

Works well on Safari and Firefox but not Chrome or IE. Could this be a webkit issue?

Boxes below the slider: http://goo.gl/5IkgSF