Could you please post a screenshot with the pertinent Panels visible?
Could something hardly noticeable (like a space) have another size than the other letters?
I can't post a screen shot, sorry, I amended the situation. I'm still unsure as to why the problem occured... I'm certain it was not a small space between lines though, I checked that first...
I did not mean an additional line, but a letter or space in the text that might have a different size.
If one selects text and no font size is indicated in the Character Panel that indicates that there is more than one size set for the selected letters.
Sounds like you have solved your problem, but for future reference, this article might be useful for posting screen-caps, and other images, to the forums: http://forums.adobe.com/thread/592070?tstart=0
Could you please post a screenshot for each type layer with the whole text selected and the Character Panel visible.
Pressing the Return key causes a line break because it ends a paragraph.
I think your text blocks each contain 4 paragraphs, with the first paragraph being wrapped onto a second line.
Look in the Paragraph panel. I think you'll find that you have a post-paragraph space of greater than 0 in the right-hand block.