Safari - Top Sites disappears after another app went rogue A few days ago an app went rogue and leaked memory taking up all 4gb of RAM and more than 8gb of page file space. The result was a machine which was unusable and took about 20 minutes to (eventually) shut down. 

After rebooting Safari would not show my "Top Sites", instead showed me a "This page could not be found" (or something similar, I can't remember), would not display the "Top Sites" button on the menu, and the button was not available in the list of buttons to add.

After a reboot this was resolved, but I would still like to know what went wrong.

Does anyone know what could have gone wrong here?
I don’t really know the right answer, but I have a guess. 

You mention that you use safari on Windows, but you don’t mention the window’s version. In any case, the extreme load your computer had (in terms of RAM/HDD) might have caused a corruption in the Safari’s config and/or cache. Your computer, in an effort (desperate!) to save its information and write to the page file, might have had problems saving all the info before the shutdown actually occurred. 

When you returned after the reboot, safari’s settings may have been corrupted preventing the TopSites button to appear. 

I don’t know much about Safari’s architecture under Windows, but on OS X if the preferences are corrupted, we simply remove them and the program regenerates them upon first start.

This is just a guess of course.

But remember that your computer was struggling to save its state when you shut it down. You had no RAM and your pagefile was enormous.