I found two posts in the forum about webpi crashing
http://forums.iis.net/p/1166225/1938580.aspx
http://forums.iis.net/t/1164964.aspx/1/10
one is about webpi crashing when using IIS Manager Users, another is about when using IIS Remote Manager
and now I use administrator account on my local pc, IIS Manager crashes everytime when I click "Products" in webpi embberded in inetmgr, but I can do it via an independent webpi program from start-all programs-microsoft web platform installer and can even install features.
my webpi version is 4.0, os is windows 2008 r2 enterprise sp1