Why do I get an error when I try to apply a theme?

For some strange reason, the theme that I created, does not want to apply to some of my projects.  I'm working on a work project, and updated my theme as I went along.  It was all fine, until I changed the Object Styles, and suddenly, out of the 7 project files I have, 3 of them wouldn't apply.  It would reach the end of its application (the little blue loading bar) and then would pop up with an error.  See below;

Like I said, it's only done it for 3 of my projects.  I also have tried applying other themes (the default ones) to the project, and they didn't work either.

I have already searched the forums and found a question that was the same as this, but regarding Captivate 7.  I tried the solution that was offered there, and it didn't work.  Link to that particular one is below;

Can't apply a new theme to Captivate 7 projects

I'd appreciate a bit of help with this, because it's got me completely mind boggled, and it's urgent as well.

Thanks.