Strange Floating Boxes in Published Storyline 2 Course

Hello!

I want to begin by saying Storyline 2 looks fantastic. It's smooth, fast and has a whole pile of new features I'm really enjoying! Great jobs guys!

However, I am experiencing an issue that I'm having trouble figuring out, and I'm wondering if some of you guys might have an idea as to why it's happening. I have a really large course, one that's over 300 slides and has over 24 MP4 animations in it. It has everything: audio, animation, slide transitions, custom fonts, drag and drops, fill in the blank, etc. As a result, it takes a long time to publish so testing this issue is a huge pain.

I'm having an issue of strange boxes appearing throughout the course, and I have no explanation for them. Below are images of what the software is showing, and what is being exported (sorry for the poor quality on the first one; a client sent it to me):

I would like to say it is just this slide, but there have been about a half dozen slides that experience this problem. It all seems to be around some kind of interaction or animation, like dragging a picture or fading in text. 

Another curious thing is that this "black box" issue doesn't show up on my computer after I upload it to the server. Now, our Internet is much faster than my client, so if this issue is related to download speed, maybe that's the reason. I thought it could be related to Flash version, but as they are using Google Chrome, I imagine their Flash is up to date.

The colour of these boxes are a consistent grey, which is the same as our website, so I'm also thinking it could be Storyline Player related as I'm using that grey there (you can't see the Page Background but it's also the same grey):

This makes me think that it's somehow related to the player. However, changing each colour and testing this, and exporting it each time will take at least 4 hours as it takes about a half hour to publish. And being this issue is sporadic, and I can't actually see it, telling the client it's fixed would be futile as it may be on one of the other 300+ slides.

Kristin Overholt from the Articulate Success Team told me via email it could be related to the memory on my computer when publishing, but my computer is fairly fast and should have more than enough memory, so I can't see this being the problem.

I've also read forums that say to make sure I'm not running off an external hard drive or memory stick when publishing the course, and I'm not.

I would attach the .story file, but the file is 712 MB, so it's probably too big to send.

If anybody could help me out, or offer me a solution, I would really appreciate it.

Thank you!

Kenton