I am using version 2010.1.415.35 but the reasoning still applies. The reason I am using this thread is that it came up first on Google so will be the one most watched and I had a similar problem to bemara57. I wanted to centre the loading image in the centre of the screen but I was using mast/content pages and a RadAjaxManagerProxy control on the content page (which doesn't have client events).
The suggested method is to use (in the content page):
RadAjaxManager = RadAjaxManager.GetCurrent(Page)
however I was getting page.init errors.
So I used (in the content page, where RadAjaxMaster is the id of the RadAjaxManager in the master page):
and everything works fine. Hope this helps someone else.