Yes, I did an upgrade from Vista, since the email from Microsoft said we could either clean install, or upgrade Vista ! Since it would take me over two days of reinstalling/configuring the softwares I use, I opted for an upgrade to test this new Windows.
Everything is working fine, just this user account empty list, which is a bug since Vista, so I am encline to think that this bug is still present in Windows 7 ! Wouldn't be better to find a fix for this ? Since I do not know what triggered this bug, it could come back even in a clean install...