Google announced on the Google Analytics blog that they are officially dropping support for Internet Explorer 8 users.
It does not mean they won't report on who is accessing your web site using IE8, but it does mean that you won't be able to see who is using your site if you are trying to do so via IE8.
In short, the Google Analytics reporting tool will not run well if you are accessing it via Internet Explorer 8.
To focus on supporting modern browsers, we are deprecating official compatibility of Google Analytics with Microsoft Internet Explorer 8 (IE8) at the end of 2013. We decided to do this to both accelerate the pace at which we can innovate new product features, and to facilitate adoption of newer web technologies in the design of the Google Analytics product. Our ultimate goal is to provide a superior user experience for every GA user. As a note, we’ll of course continue to measure traffic from IE8 browsers to your website.
When? You got at least 3 months. Why so long? Well, many companies still are on Windows XP and use IE8.
Forum discussion at WebmasterWorld.