I've had this happen before, and not sure of the exact circumstances the first time, but last night I was trying to post up a layout (centered text) and the plugin hides my text and turns it into a pop-up link to the Simple Share Buttons Adder website.
The exact code I was using last night was:
<div align="center"><b><span style="color: #ff0000;">** ALL AGES WELCOME **</span></b></div> <div align="center"><img alt="[IMG]" src="http://www.halodiehards.net/wp-content/uploads/2013/04/spartans-playground-banner.png" /></div> <div style="text-align: center;" align="center"><b><span style="color: #ff0000;">** ALL AGES WELCOME **</span></b></div>
The "** ALL AGES WELCOME **" above and below the image would not show up unless you hovered over the image or the areas where the missing text would be, then it would pop up in a box as the Plugin site link.
The only way I could get it to work without this behavior was to delete the code that made the text red. Make it red, and the text disappears and turns into the link to the plugin page again.