Under specific circumstances an Access Violation could indeed occur.
This has now been fixed.
Please note that TAdvBoxNetDrive functions a little different than TAdvDropBox because of the way the Box API works.
You'll first have to call AdvBoxNetDrive.GetFolderInfo to retrieve a list of files and folders, then select the specific Folder you wan to upload files to from the AdvBoxNetDrive.BoxNetDrive collection.
A general example for this technique can be found in the CloudStorageDemo application (included with the product download).