I have discovered a bug on NSIS.. I hope you can reproduce it on your machine.
When I comment everything on config.h but the BGBG and the unistaller.. there is no problem. The problem comes when I only left the BGBG or the unistaller or neither. For instance, the problems occur when commenting everything on config.h.
The problem is that when I put DirShow to the "Show" value, and the $INSTDIR is well (with .onVerifyInstDir). In that moment, the installer cant reach the intallfiles section. On the instdirsection, I press "Next" and I go back to the component section. (Like the back button).
I'm using Windows 2000, Visual Dev Studio 6.0, NSIS 1.42