Having 2 Gmail accounts (or a Gmail and a Google Apps account) logged into the same browser can cause problems. Especially if you are using Google Calendar, Documents or Drive. Here’s how you can add another user to Chrome and make sure the two Gmail accounts don’t conflict with each other.
Note – in the latest version of Chrome, look for “Profiles” in the top menu bar (between Bookmarks and Tab). “Profiles” replaces “People” in this video.