Sometimes when troubleshooting aspects of programs or OS features, we may assume some things are not related to the problem we are experiencing, either by dismissing them or more commonly by just overlooking them as a potential contributor to the problem at hand.
MacFixIt reader "Mark" contacted us regarding a problem with some features of Safari, including that the Top Sites and the Cover Flow of the browser history were not working. Initial troubleshooting efforts included reinstalling the system software along with graphics drivers for his third-party graphics card, and removing preferences and plug-ins; however, none of these efforts helped the situation.
It turns out, the problem happened because of some faulty graphic driver settings that were preventing Safari's "Top Sites" feature from working, and was found when the system profiler listed "Quartz Extreme" as not being enabled for the active display. This could have been caused by the third-party drivers and video card being used, but also could be from numerous other applications, system add-ons, or other modifications. In this case, toggling between different display modes corrected the faulty driver settings and fixed the issue.
Though Safari's "Top Sites" feature does not require Quartz Extreme in order to run (just boot into Safe Mode to try it out), it may require some other GPU or graphics driver features to be enabled, such as specific OpenGL functions that could be disabled with a driver error. The specifics are unclear, however, it is worth noting that a seemingly unrelated item such as a graphics driver problem could affect a program's features.
In this instance, the Quartz Extreme feature being disabled was indicative of a deeper problem with the graphics drivers, which in turn were affecting Safari and perhaps other programs. Keep your mind open when tackling various problems, and be sure when troubleshooting to not dismiss every aspect of your system as a potential contributor to the problem at hand. Try numerous angles and approaches, even if you think they may not be related.