Summary pretty much says it. I've set USE=-pam and whatever I do I cannot login with qingy. I even created a passwordless user and qingy fails. Any more info I could provide?
the bug report page told you to attach `emerge info` which you neglected to do also, are any errors shown ? is there anything in your system logs (/var/log/) ?
This is a known bug in qingy, and is already fixed in CVS. Next version will be OK...
Fixed version is now in Portage...