Hello, In the option bar, right-click on the T icon on the left side, and select reset tool.
If this does not work, you should delete the fonts you have, then download it from the official project page: http://sourceforge.net/adobe/sourcesans/wiki/Home/ and restart your machine.
Thank you for the reply. I know Source Sans is similar than Open Sans, but I have to work with Open Sans because the PSDs need to be consistent, and I don't want to change the font family in all files. (about 35)
I think the problem was with the previous font, so I needed to update all layers in the PSDs. Btw the font size with the 'new' font became same with 13px size.
What is the most common property for the fonts? Sharp, Smooth? I have MAC and MAC LCD too.