Origin won't launch after update

[boingzoom]

After updating to the latest version of Origin (9.2.1.4399, the client won't open. I get black dos box pop up briefly, and then and then nothing. I tried running an Origin game - Mass Effect 3 - and the same thing happens. I tried restarting my computer, and no difference. I uninstalled Origin, re-downloaded the installer, ran it and ran the updater, and still nothing. Everything was functional before updating. 

OS: Windows XP SP3