I've got the same problem. Errno 11 is because too much data, sending is in progress.
Fix is easy: assign a non zero value to the writeTimeout property of your serial objet. Then the write method will wait up to this time for sending data.
Note that writeTimeout is new in PySerial v2.1, released 2004 July 28.
-Peter -- http://mail.python.org/mailman/listinfo/python-list
