[web2py] occasional portalocker errors

[mr.freeze]

I get this occasionally on Windows 7 and Python 2.5:

Traceback (most recent call last):
  File "C:\web2py\gluon\restricted.py", line 188, in restricted
    exec ccode in environment
  File "C:/web2py/applications/test/models/db.py", line 66, in
<module>
    Field('converter')
  File "C:\web2py\gluon\sql.py", line 1380, in define_table
    t._create(migrate=migrate, fake_migrate=fake_migrate)
  File "C:\web2py\gluon\sql.py", line 1856, in _create
    portalocker.unlock(tfile)
  File "C:\web2py\gluon\portalocker.py", line 78, in unlock
    msvcrt.locking(file.fileno(), mode, os.path.getsize(file.name))
IOError: [Errno 13] Permission denied

I reload the page and it goes away for a while.