White Icons

Hi. I've just started using Zoho Mail and it seems really good. I have 1 problem though. When I view my mail from my home computer, all the icons are white making them very hard to see. On my work computer they are fine. I've been looking through the settings but can't seem to find what needs to be changed. Can anybody help?

I'm using Firefox on Linux (Fedora 7). I've also installed the themes as you can see in the attachment but have still got the problem. :(