I had a problem while updating my system.
Tha add/remove complementary package was taller (see image : http://imageshack.us/photo/my-images/834/packagekitvalidation.png/ ).
Isn't it possible to make this window resizeable ?
We moved the upstream bugtracker to GitHub a long time ago. If this issue still affects you please re-create the issue here: https://github.com/hughsie/PackageKit/issues
Sorry for the impersonal message, and fingers crossed your issue no longer happens. Thanks.