I today solved the mystery!
For a long time, it has appeared as if when I deployed a newly built application from VS2010, it somehow erased a (any!) previous application that I installed the same way. It was pretty consistent – only 1 application at the time it seemed! Come on – what’s that about?
The reason (as I learned), is that each application carries a unique ProductID (see below), which uniquely identifies the application to the phone. As Visual Studio does not generate a new unique ID on launch when you go “File – New…”; I was effectively reusing the same ProductID and replacing the existing (old) application on the phone.
How to solve this?
1) Open Guid Generator
2) Create a new GUID (Registry style)
3) Replace the exiting default ProductID with the newly generated version (2)
4) You are good to go!