Connection points on the line are unevenly distributed

I'm trying to create a very basic link sequence diagram in Visio 2013, but the connection points on the life lines are unevenly distributed, making it impossible to create a beautiful diagram. According to many examples found on the internet, the points should be evenly spaced. I just installed Visio, so this is a fresh install.

Does anyone know what is causing this and how to fix it?

I cannot include the image due to my reputation (just started here), so here it is:

http://i.imgur.com/Cf1StsR.jpg