When I want to debug in VS 2012, F10 is not stepping over a single line but most of the time continues like F5. As I've seen in the internet, this is an old issue, and for VS 2008/2010 there are Hotfixes availiable.
I'm programming mainly C# (ASP.NET with IISExpress).
In order to repro the error, you might want to connect to my developer machine:
RDP:owl.winhost4you.com:9058 (You might need to start mstsc /admin, because there is no license server configured.)
Please contact me for an admin login at firstname.lastname@example.org