This is embarrassing. It is a file not found problem with my XNA + Silverlight project.
I'm modifying the "My Little Teapot" XNA + Silverlight sample for Windows Phone 7, at http://msdn.microsoft.com/en-us/library/ff431744%28v=vs.92%29.aspx and am getting a File Not Found error in OnNavigatedTo() when I merely try to load a texture:
myTex = content.Load("tex1");
(You'll notice this isn't the usual file not found question where the coder is trying to load "tex1.png" instead of "tex1".)
My solution has the same project as in the sample, "sdkMyLittleTeapotCS", and a content project I added, "my content". I added "tex1.png" to the "my content" project, and its asset name is indeed "tex1". Its build action is set to "Compile", and I've tried setting the "Copy to Output Directory" settings to "Do not copy" (which is what works in my normal XNA projects) and also to "Copy if newer".
In all cases I get an exception with a file not found. What is this idiot doing wrong? Thanks in advance!