The easiest way to solve this issue is to register your Tooth Atlas from either the Comparisons page or Morphology page.

To navigate to one of these pages, choose a tooth from the Table of Contents then choose Comparisons or Morphology from the top of the page.

This issue will only occur for users with certain, outdated java versions.  (Java versions 1.6.0_27 and above should not experience this issue)

Windows users:

1. go to google.com in Internet Explorer and enter the following search phrase:   "java check version"
2. the first result should bring you to a page at Oracle.com that will check your java version
3. follow the instructions to make sure you have the latest version of java for Internet Explorer