I have some short USB 2.0 extension cables that I use to plug between the Macbook and USB 3 devices - to reduce them to USB 2.0. Because if I for example try to copy more than a few MB to a USB 3 external HD, the Mac freezes. Every single time. So that's working well then.
Try different powered hubs. Last week I discovered a USB key that eats so much power it won't run without a powered hub! Numerous external hard drives and optical drives are in this camp, too.