Some sort of graphic related problem with Minefield nightly builds. I'm not an expert, but it looks like the problem is with semi transparent pixel drawing. Might this be related with graphics hardware? Here is the screenshot, how it looks: http://img148.imageshack.us/img148/2536/ffinterface1.png In the picture the problem is well seen on the TAB headers and vertical line with a pattern in a page illustrates the problem in displaying transparent elements in page content. When interactive interface elements are mouseovered (paticularly "close tab" buton), the distortion around changes.