Captions on Images Keep Deleting

Good afternoon,

When I upload pictures to my media library, I give them a caption. The images have those captions “pop-up” when you hover over them in the portfolios I’ve created. Here’s an example:
http://jamestiffinjr.com/portfolio/afterschool-junior-robotics/gallery/tales-not-yet-told/

I’ve done that with all of my images and portfolios, but for some unknown reason, entire images sets (as associated with my portfolios) will lose their captions. This one I just created the other day, and today I went and looked at it and found that all of them were gone:
http://jamestiffinjr.com/portfolio/creating-the-reflector-deflector-bird-protector/gallery/tales-not-yet-told/

It has happened in the past, and I just chalked it up to something that I did wrong, but now it has gotten to the point of frustration. I was trying to create a blog post that used some of the images from the second portfolio I shared above, and I discovered that the caption are all gone.

Do I need to add the captions at a different place, and not when I’m initially uploading them? Should I do it when I make the gallery? Do I have to do it for each image by visiting them within my library.

Or is this an entirely different problem?

Thanks to anyone who can help me out here, and lower my frustration level. 🙂