Formatting causes text not to display in pop-ups

I'm currently working in RoboHelp 8.

I've created a topic I would like to have appear in a pop-up in an image map. These occur very frequently in my Help file, usually with no problem. However, this topic has various formatting, including italics and colored text. When I create the pop-up and View Selected Item, some of the formatted text does not appear. (The topic itself shows up perfectly in View Selected Item - this problem only occurs when I view it in the pop-up on the image map.)

This has been going on for years and I've worked around it by removing the formatting that seems to cause the problem - but I'd really like the formatting to remain. The frustrating part is that this doesn't always happen - I can't find a consistent problem. It has just happened again, and I hope you can help me with this.

Here are some pictures that I hope help explain the problem:

The topic in RoboHelp Design view.

Picture 1a: The topic in View Selected Item view - note that everything looks fine.

Picture 2: The topic as it appears in the pop-up in View Selected Item. Note missing text in italics and blue. It seems to be there somewhere, based on the spacing - but it seems blank.

Picture 3: The topic html. Don't know if you can read this.

Please let me know if you need any further information - I may not have explained this very well.

Thanks so much.