USB ethernet (smsc95xx) transmit timeout errors

We are seeing some 'transmit timeout' errors from the smsc95xx driver.
I've found references to similar problems on the RPI, but no explicit
resolution.

Our systems are Intel i7 motherboards with the USB chip on a 'front panel'
board (together with three USB2 sockets) plugged into one on the
motherboard's USB3 sockets.
(The silicon has some kind of clever USB hub in it.)

Initial failures were with the 3.2 kernel from Ubuntu 12.04, but I've
updated one of the systems that failed to a 3.8 kernel and it still
fails.

Does this problem 'ring a bell' with anyone? and is it likely to have
been fixed in a more recent kernel?

Even with heavy traffic the systems might run for 24 hours before
failing - so proving a system is 'fixed' is difficult.

	David