Microsoft released a "recommended update" for all Internet Explorer 9 Beta customers via Windows Update. The KB2448827 includes stability fixes for the beta build.
Another update shipped today KB2452648 resolves issues between the IE9 send feedback feature on 64-bit machines with Windows-Live-Essentials 11.
Customers who have automatic updating enabled willn't need to take any action because this update will be downloaded and installed automatically. Customers who've not enabled automatic updating need to check for updates and install this update manually.
For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.