Silverlight 3 has been updated with a small set of bug fixes and support for the GB18030 code page for developing Chinese localized applications. A GDR, unlike a hotfix update that you might get from product support, is intended for general use but is much more narrowly scoped and often much smaller in scale than the more widely known service pack releases. As you might guess from the title, this’s actually the second GDR update for Silverlight 3. I didn’t mention the first GDR because it was a runtime only update (it primarily was to fix a problem with media buffering), announced.
More info: Download