shutil: permission denied errors on windows

[Antoine De Groote]

Google tells quite some things about it, but none of them are satisfactory.

I'm on Windows, and shutil operations (e.g. move, copy) throw [Errno 13] 
Permission denied all the time, for the source files. It seems that this 
is the case for all my files. But what I don't understand is that 
yesterday it still worked. I didn't change anything on my system though 
(at least not that I am aware of). I restarted the computer several 
times to see if that helped, but it didn't. Also I can't find a process 
that would be using the files...

Has anybody experienced this problem before, or have a solution?

Kind regards,
antoine

Here's the code that throws the errors

[...]
for l in files:
             from_file = os.path.join(dir, l)
             to_file = from_file.replace(tree_top, backup_dir)
             try:
                 if not os.path.exists(to_file):
                     log('Copying new      %s' % from_file)
                     counter_new += 1
                     shutil.copy2(from_file, to_file)
                 elif int(os.path.getmtime(from_file)) > 
int(os.path.getmtime(to_file)):
                     log('Copying modified %s' % from_file)
                     counter_mod += 1
                     shutil.copy2(from_file, to_file)
                 elif os.path.getsize(from_file) > os.path.getsize(to_file):
                     log('Sizes differ, but not rest: Copying %s' % 
from_file)
                     counter_special += 1
                     shutil.copy2(from_file, to_file)
                 elif os.path.getsize(from_file) < os.path.getsize(to_file):
                     log('Orig file smaller than backup file: Copying 
%s' % from_file)
                     counter_special += 1
                     shutil.copy2(to_file, backup_dir+'DIFF_SIZE')
                     shutil.copy2(from_file, to_file)
                 else:
                     #log('not treated: %s' % l)
                     pass

             except (OSError, IOError), e:
                 not_accessible += 1
                 print e
[...]