A quick hint for those using the Safari 4 Beta in Mac OS X and wondering why Google Mail (with Gears from Safari 3) doesn’t work anymore.
Opening Gmail with an old version Gears enabled resulted in a blank white window. Disabling it brought Gmail back but, obviously, without the offline features. An updated version of Gears has been available for a while now, but the process of updating isn’t really obvious and just re-installing/updating Gears didn’t work for me for some reason.