After playing around with your slideshows and some that I created, I found the magic combination. Let's see if this is what you are experiencing.
EasyWorship is set to use the PowerPoint application instead of viewer. (This doesn't happen with viewer 2010, but Viewer won't loop slideshows)
Go live with PowerPoint 2010 slideshow.
While it's transitioning into a slide, go live with a song.
You'll find that PowerPoint will crash.
There are only two workarounds that I can find at this time.
Click the black or logo button before going live with the next item in the schedule, or take out the transitions in the slideshow.
I tested 2010 slideshows. I saved a slideshow to 2003 format and still got the error. I tried a slideshow built in PowerPoint 2007 and it still did it.
PowerPoint 2010 substitutes its transitions for the older style transition. I haven't seen this happen with PowerPoint 2007 or earlier.
You might be able to save them as 2003 format files and run them using PowerPoint viewer 2007, but you won't get the pretty new transitions from PowerPoint 2010.
Another option is to run your looping slideshow directly through PowerPoint.
When you are ready to start service, switch over to EW and allow EW to use the 2010 viewer for the sermon and other slideshows that don't need to loop.