Wouldn't it be better if you only ignored the 'illegal seek' error
instead of ignoring any ioerror (should it even be always discarded) ? I
get a 'bad file descriptor' under Windows 7, but, again, can it be
always discarded ? 

You can also reproduce the problem without using wave:

>>> import sys
>>> sys.stdout.tell()

I'm really unsure about the proposed patch.