Problem with pasting text in textbox

When I paste text into a textbox, if fills to the left edge of the textbox, but the right side appears to have an invisible margin. Sometimes it's a half-inch wide, other times it's half of the width of the textbox. I've been copying text from Word documents, but the same thing happens when I pull random text from the web. However, if I just type information into a textbox, it works fine. I've looked at "invisibles," but don't see any obvious problems. Suggestions?

I've attached two samples: the first after pasting text and the second after trying to justify the same text.

Thanks,

Churrosychoco