Thanks for the tip... I fixed my extension and have included it below for anyone else that wishes to use it.
1. Download, extract, open in dev studio
3. Copy TelerikExt.dll to the bin folder of your Web project
4. Open windows explorer
5. Find the dll (in the bin folder) and drag it to Microsoft Visual Studio, dropping it on the toolbox (in to the "RadControls 'Prometheus'" toolbox folder.
6. Move your "RadAjaxManager" to the top level of your site (master page or main .aspx)
7. Open any sub pages (content ASPX or user controls)
8. From the toolbox, drop an instance of the RadAjaxManagerProxy on your page
9. Configure it exactly as you would the normal RadAjaxManager
At runtime, the RadAjaxManagerProxy will translate all local control IDs to UniqueIDs, then pass them off to the main RadAjaxManager, then disable/hide itself to ensure there is only one RadAjaxManager per page.