Hi, thanks for posting and I'm glad your enjoying NCrunch!
NCrunch will only perform builds and run tests within a workspace it has created for itself, so if you're experiencing file locking problems inside your solution, there is a high likelihood that you have absolute file path references somewhere in your solution that are pointing to a fixed part of your drive (and within the folder you are trying to rename).
When using NCrunch, make sure that ALL file references within your source code are using relative paths. One way you can test for this is by closing down your IDE, renaming your solution folder, then reloading your IDE and trying to build/run tests.