Last week, my Microsoft Auto-Updater alerted me to the release of the Office for Mac 12.2.0 Service Pack. Since I upgraded, I have had constant crashes in PowerPoint when opening PPTX files.
After a week of puzzling, I opened a WMV video in Firefox 3.5.1 and the browser immediately crashed. As it happens, I have Flip4Mac Studio installed so I went to System Preferences to see if anything was amiss. The Flip4Mac preferences applet immediately exited.
To cut a long story short, I solved both my PowerPoint crash and my Firefox crash by re-installing Flip4Mac. It seems that the Office service pack updated (broke) the Flip4Mac install on my machine and this causes a crash in every app that uses WMV video.
Since I use a lot of embedded video in PowerPoint, the broken Flip4Mac install caused a crash every time.
The short answer: download and re-install Flip4Mac - problem solved.