I created an account on the pubcenter about 4 or 5 weeks ago, and have never been able to get the Ad Control working. Last night i created a new VS2010 project and just added an AdControl.
If i use the test details, i now get the test banner appearing. If i use my app details, i get nothing, not even the outline of the AdControl. No errors are logged in Visual Studio either, its like the AdControl is not there.
You won't get an outline of the control in error scenarios except perhaps in rare instances where the ad graphic is missing and the border is turned on.
The latest ad sdk won't display live ads in the emulator - only on a device. Are you testing in the emulator?
Also note that in some countries pubCenter does not serve ads - although you seem to be American, so that's probably not it.
The SDK won't work properly if you don't have the correct set of ID_CAP_<name> capabilities listed in your WMAppManifest.xml file - check that you've specified all of the one's required in the SDK documentation.
Those are the main reasons why ads wouldn't show after such a long time of creating your account - unless your app id or ad-unit ids are wrong.