So, after Lars pointed me to the right direction, I think I managed to perfectly align widgets with checkbox labels. The next blog post will give the full details, but before that I have a small design question... Is it just me or the group labels are now visually redundant?
What do you think? Should I eliminate the labels or keep them for consistency with other windows?
By the way, I am aware that the entire authentication group should technically be inside the general group, but I couldn't figure out how to do this without making the layout look very unbalanced. Specially now that I'm aligning the widgets with the checkbox labels. Suggestions are welcome.