Which version of Cairngorm?
The older versions caused havoc when mixed with modules. Chief of the problems was the Front Controller instantiating commands from modules and preventing them from being garbage collected properly.
You also run into problems where you need to load the modules into the main app domain to get Cairngorm to work the way you expect it to, which also prevents modules from being garbage collected.
I don't know if anyone these problems have been sorted in later versions.