Tim, your code worked fine without crashing on my system.
It will only close the file if both excel files are in the same taskbar
window.
In the past I have seen some users' excel act quirky when closing a
file, the following code convention seemed to be the most stable for
me:

Application.DisplayAlerts = False
Workbooks(w.Name).Close SaveChanges:=False
Application.DisplayAlerts = True

Goodluck-Lonnie