That probably hints at a bad port and/or cable, making the USB negotiation wonky.
You can check the syslog (run
logread in a shell; the matching excerpt from the kernel log might also be helpful, so launching
klogd beforehand will take care of that) to see how badly it's misdetected.
This is mostly a hardware issue, the main difference may be that I'm overly cautious, in order to avoid the numerous "oh, hey, I just thrashed your filesystem" issues that could otherwise be caused by USBMS

.