Serial error

I use brickpi to control a pair of motor for a line following robot and it works well, but from now when I send BrickPiUpdateValues() it returns this error:
IOError: [Errno 5] Input/output error

I code in python

Can snyone help me?

Hello Simone,
Can you tell us a little more: Are you using the Dexter Industries image? Was this working before and now not working? Is the error returned sporadically or does the BrickPi throw the error all the time?

Thanks, John