It appears that Dynamics CRM Online does not play well with Internet Explorer 10. In fact, it downright does not work with IE10. Many of the web dialogs are unusable and when you receive an error, the error dialog exhibits bazaar behavior.
This is an absolute tragedy. Windows 8 launched 3 weeks ago with IE10 included and the Dynamics product team was not prepared. The user experience on a windows 8 machine for Dynamics CRM is basically unusable.
However, there is an easy way to fix this. For IE10, hit ALT. Then go to Tools -> Compatibility View Settings.
Then add your CRM Online URL to the list. Below I am using the default dynamics.com domain. This will force IE10 to render the CRM application in compatibility mode.
Maybe Microsoft should make dynamics.com automatically render in compatibility mode? Or would that be too big of a black eye?