Hello, Recently, some colors in my Mac OS 10.7 have become transparent (or white, I don't really know). For example : - any zebra striping is invisible (e.g. Finder in list view, any file opening Dialog, Thunderbird's message list, etc.) - in Thunderbird, in the "new message" window, the area containing the "from" address, "to" address and subject doesn't have its usual gray background anymore, it's now white. - in some websites, some colors are transparent. For instance, I can't see any zebra striping here : http://www.financefi.fr/trackers/liste.php (tested with Firefox, Safari, and Opera) - I am running Windows 7 in a virtual Machine, with the same problems (the above webpage's striping is invisible in IE9). BUT, these invisible colors get revealed when I hover above them with any semi-transparent overlay, like any other windows' drop shadow (see screenshot below), the background of the app switching area (Cmd+Tab), etc. Can it be related to my upgrading from 10.6 to 10.7 two weeks ago? I can't tell for sure when it began exactly... Thanks for any help!