Double logo issue

I uploaded a custom logo of recommended size (314 x 50px interlaced PNG) and everything looked good in Firefox. But when I looked at the site in Internet Explorer or accessed it through a mobile device, there is an issue of Irex default logo (dark red) showing up at the bottom of my custom logo (looks like it overlapping).
I really like the theme, and I would like to keep it for my site. Please help to resolve the issue.