Your template is restyling the background. You'll need to inspect it with Firebug for Firefox to find the CSS that's causing it. It uses the same styling as the tooltips seen when mousing over an "i" icon next to a field in profile edit. Below are the classes for its backgrounds.
cb-tips-bg
cb-tips-fg
If using a custom CB template it could also be simply missing the classes, which if is the case please compare your templates CSS to CBs default template CSS.