Just an FYI post to anyone that might be developing PyHamilton in the future. When trying to save changes to the STAR_OEM_noFan.med I kept encountering this error.
After a good 30 minutes of trying to figure out why this was happening, I realized that I still had Run Control open… 
Run Control was of course accessing the files which I was attempting to change, hence the sharing violation.
Moral of the story: close Run Control!