To date, I've been running everything through XAMPP htdocs on my Windows 7 computer.
While trying to resolve this issue, I have added the BulletProof Security plugin, which lists permissions for a few of the files and folders used in WordPress. As part of the installation, htaccess was added to my root WordPress directory, among other files throughout the system. BulletProof claims that my system is working correctly, and lists a number of files and folders along with their permission settings in the standard 3-digit format. None are currently set according to BPS recommendations. The classes folder and dispatcher.php are NOT included in the BPS table.
Most of the info I've seen suggests that file permissions is best handled through FileZilla, an FTP server program. I've since installed FileZilla, and have created an ftp site on my local computer. I receive a 504 error when trying to set permissions on files I copy to the ftp folder; apparently, my version of Windows does not change permissions in this way even with FileZilla. I am doing everything from my home computer; I have administrator priviledges for all files and folders, and so far as I can tell, after reading about others' experiences with FileZilla on Windows computers, permissions are actually supposed to be set by right clicking on a file or folder -> Properties, and unchecking the Attributes:Read-Only checkbox without any need for FileZilla. This action DOES NOT work. Advice on changing permissions is needed.
The dispatcher.php file DOES include code that seems OK.
Still stuck on this... thank you for your help so far, Alexey!