We've had problems with "USB 2" cables that really aren't, causing debug problems.
Just because it has a stamp or moulding on it doesn't mean it works. There's lots of cheap and bad cables out there.
Try as many different cables as you can find. Look for any cables that came with "quality" or branded products.
If you do find below-spec USB cables that cause you problems, don't keep them, they'll only give you grief later.
Tom