Motion 3
Running G5 Powermac and Motion 3. Why do I getting the spinning colored beach ball when working with motion 3 all the time?
PowerMac G5/AppleTV 1&2/iPhone 4/iPad 2, Mac OS X (10.5.7), 2 ghz/4 gb of RAM
Insufficient info even to take a guess.
If it happens for all – not just one – projects, I'd probably try the first lines of troubleshooting: repair permissions in Disk Utility and trash preferences (use Digital Rebellion;s app).