I checked out some mxml / action script code from our CVS repository today and recieved an error when trying to compile it:

 Error: Type was not found or was not a compile-time constant: <ActionScript Class Name>

It seemed from the error message that someone must have 1) forgotten to add an import in action script or 2) had messed up with the xml namespace attribute in the mxml file or 3) maybe they forgot to add the actionscript file to cvs.  After double checking each of these possibilities, I found that none of them was the problem.  Actually I was getting this same error message for several different actionscript classes.  So then I started asking the developers who wrote the code why I couldn’t compile it, they simply said it does compile just fine on their machines.  Yet, it still didn’t work on my computer.  After stepping through the imports and xml namespaces and showing one of the developers that the actionscript source code’s file was indeed on my computer, he noticed that one of the folders in the path to the file had an incorrect upper case letter in it.  I had checked this code out from cvs and for some reason cvs had created one of the folders with an upper case letter which was not in the package name. 

Here is an example of the problem:

Action script class’s package name: