Messagebox causes Windows to lose focus on the application

I have just started using VS 2006 and the 2.0 framework. Formerly, I used msgbox and usually only specified the message string. Now I’m using messagebox.show and the full set of parameters (message, caption, yesnomaybe, etc). When the user dismisses the messagebox, whether by mouse or by hitting enter, the app minimizes, unless it’s the only app on screen. I don’t remember ever having this problem with the 1.1 framework.