Are you using one of the 2013 templates?
If so in 2007 apply one of the 2007 ones and see if the animations work again. Or download the free 2010 viewer and use that to show the presentation.
If you used the facet template have a read here.
http://www.pptalchemy.co.uk/PowerPoi...ion_Fails.html
The solution may also apply to other 2013 templates - some of the coding is pretty sloppy!