I don't know Macs at all so my apologies in advance if I'm talking a load of rubbish.
In Windows we have the option to carry out a System Restore to turn back the system to a time and date before something happened. That something could be updating.
Does your OS X have anything similar?
In any case I am alerting your post to Pete, (MrMacfixit), who knows 'everything' about Macs. Hopefully he can give better advice.
Mark
I have a Mac with OS X Snow Leopard and haven't yet upgraded to Lion but as a recent Apple System Update it said it had an update to Safari. It installed Safari as part of that update process but now Safari won't open at all. When I click on it it bounces in the dock like it's opening and even I go up to the Apple menu and select Force Quit it is listed as being open but yet Safari itself never appears to fully open. For example there is no actual window/web browser.I even went to Apple's website to redownload Safari and made sure I selected the Snow Leopard version and did a reinstall but it still won't open.Any idea of how I can fix it? I use Firefox a lot but still like to use Safari since it syncs with my iPhone bookmarks.

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