Our records show that you purchased RadControls for Silverlight Developer Licenses. The Developer Licnese includes free service packs for the version you hold and Stnadrt Support package. In order to receive our latest major version release (Q1 2009) you need to upgrdae your Developer License to a Developer License with Subscription. Your upgrade options are listed in your account -> Renewals and Upgrades.
I hope this helps. Let me know if I can assist you further.