Why is HttpNotificationChannel.Open throwing ArgumentException() E_INVALIDARG? - windows-phone-7

Question

Here is my code. Everything works fine the first time I run it, i.e. HttpNotificationChannel.Find() returns null.
But the second time I run it, Find() returns the proper thing, however when I get to the Open() call, it throws an exception. Which is really odd, since Open() doesn't take any arguments.
What am I doing wrong?
public string ChannelName = "MyAppChannel";
...
NotificationChannel = HttpNotificationChannel.Find(ChannelName);
if (NotificationChannel == null)
{
NotificationChannel = new HttpNotificationChannel(ChannelName);
}
NotificationChannel.ChannelUriUpdated += new EventHandler(Channel_ChannelUriUpdated);
NotificationChannel.HttpNotificationReceived += new EventHandler(NotificationChannel_HttpNotificationReceived);
NotificationChannel.ErrorOccurred += new EventHandler(Channel_ErrorOccurred);
NotificationChannel.Open(); // <-- Kaboom here, the 2nd time
Here's the full text and stack:
System.ArgumentException: E_INVALIDARG
at Microsoft.Phone.Notification.SafeNativeMethods.ThrowExceptionFromHResult(Int32 hr, Exception defaultException, NotificationType type)
at Microsoft.Phone.Notification.HttpNotificationChannel.Open()
at LiveShare.NotificationManager.Initialize()
at LiveShare.App..ctor()
at System.Reflection.RuntimeConstructorInfo.InternalInvoke(RuntimeConstructorInfo rtci, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture, Boolean isBinderDefault, Assembly caller, Boolean verifyAccess, StackCrawlMark& stackMark)
at System.Reflection.RuntimeConstructorInfo.InternalInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, StackCrawlMark& stackMark)
at System.Reflection.ConstructorInfo.Invoke(Object[] parameters)
at MS.Internal.TypeProxy.<>c__DisplayClass30.b__2a()
at MS.Internal.TypeProxy.CreateInstance(UInt32 customTypeId)
at MS.Internal.FrameworkCallbacks.CreateKnownObject(IntPtr nativeRootPeer, UInt32 customTypeId, String initializationString, IntPtr& nativePeer, UInt32 isCreatedByParser)
at MS.Internal.FrameworkCallbacks.CreateUnknownObject(String assemblyName, String typeName, IntPtr nativeRootPeer, String initializationString, UInt32& customTypeId, UInt32& coreTypeId, UInt32& typeFlags, IntPtr& nativePeer)

Answer 1

The correct solution is not to call Open() if Find() succeeds.

Answer 2

This looks very similar to a documented problem with the CTP as described by Nick Harris last April.
Solution: If you try to Open a channel almost immediately after you hit Debug when emulator fires up this issue will occur. The solution is simple – Give the emulator two minutes before making the call.
In case that's not it, there's a good article on Silverlight Show that covers push notifications in a WP7 stock quote app.