Sorry to hear you're having trouble. In this case, I -think- (I'll have to verify) that it is not possible to have GridButtonColumns (or buttons in general) fire a PostBack when binding to web services. The whole idea with web services is that you're sending JSON over the wire and building the UI client-side ("clean, client-side HTML"). As such, I don't think the HTML rendered after client-side binding includes the hooks for ASP.NET page postbacks.
If you need the PostBack, I'd suggest using a RadGrid bound "normally" to a ObjectDataSource or SqlDataSource and then using RadAjaxManager to optimize the user experience. It won't be as efficient over the wire as web services, but it will be much easier to use PostBack actions if you need them.
Hope that insight helps. If you get stuck, let me know and I'll be happy to assist.