WP8 - Changing splash screen from default causes app to crash after splash screen

So I'm working in Unity 4.2.1 and building for Windows Phone 8. The game runs fine, all the native code for the device runs fine (back button, live tiles, etc) so now it's time to spruce it up a bit with a nice splash screen!

As soon as I override the default SplashScreenImage.jpg in the Visual Studio project with my own .jpg file, building and running the app causes problems. The new image displays briefly on screen (~1-2 seconds) before a black screen shows (as it always does currently). However, nothing proceeds to happen from then on. Eventually the console periodically receives the error "thread (random hex) exited with code 259".

Does anyone know what is going on here? I have searched the internet for this problem but haven't come across anything similar. MSDN docs state that the code means "No more data is available" but this doesn't really help much. Also, the image does have it's Build Action set to Content.

Any idea would be welcome,

Thanks

Fib