To reproduce bug:
1) Download http://downloads.sourceforge.net/gladewin32/gtk-dev-2.12.9-win32-2.exe?use_mirror=heanet
2) Perform installation.
Done! You have your PATH environment variable to be
Logged In: YES
I made some tests, and the bug happens only for long PATH values. Mine was 1257 characters long.
I can confirm this.