When something really messes up Chrome, being logged into your Google account and having Chrome sync settings makes repairing things pretty painless.
Recently, I couldn't get my LastPass Chrome extension to log into my LastPass account. Since I rely heavily on LastPass to handle various website credentials, I'm handicapped if I can't get it working in the browser extension.
I tried a number of things, including removing and reinstalling the Chrome extension. However, the only thing that solved the problem was to reset Chrome completely. Fortunately, I could restart the browser, log into Google and wait a few minutes for everything (default home pages, bookmarks, browser extensions, etc.) to sync. In this particular case, I had to add the LastPass extension again since the last sync must have been when I had it removed while trying to troubleshoot this problem. The reset fixed the problem and the sync brought me back to my standard Chrome configuration.