Hi Rick,
Thanks for the reply. When I get this error, AE works fine except when you move the playhead on the timeline with the missing asset, then the warning pops back up. In the project window it doesn't matter if there is a missing asset, only when it's placed in a comp. I just tried the one asset test and I get the same result. It also doesn't matter what type of asset it is.
AE 2014.1.1
Mac OS 10.9.4
2014 Mac Pro
3.5 GHz 6-Core Intel Xeon E5
32GB RAM