RadToolTipManager cannot find custom embedded skin, when a custom skin DLL is created with the Skins assembly builder (http://skinsassemblybuilder.telerik.com/). Steps to reproduce: 1. Create a custom skin and wownload ZIP from Visual Style Builder (http://skinsassemblybuilder.telerik.com/) 2. Upload ZIP to Skins Assembly builder (http://skinsassemblybuilder.telerik.com/) 3. Create new project with Telerik template, turn off all options (like additional skins). 4. Add downloaded DLL as project reference. 5. Add to web.config: <add key="Telerik.Skin" value="My_Skin" /> <add key="Telerik.EnableEmbeddedSkins" value="true" /> <add key="Telerik.EnableEmbeddedBaseStylesheet" value="true" /> <add key="Telerik.Web.SkinsAssembly" value="My_Skin"/> 6. In Default.aspx, add <telerik:RadToolTipManager runat="server"></telerik:RadToolTipManager> Result: an Internal Server Error is thrown: Telerik.Web.UI.RadToolTipManager with ID='ctl03' was unable to find an embedded skin with the name 'My_Skin'. Please, make sure that the skin name is spelled correctly and that you have added a reference to the Telerik.Web.UI.Skins.dll assembly in your project. If you want to use a custom skin, set EnableEmbeddedSkins=false.