USB is great, mainly because it’s hot-pluggable. Lots of today’s computers have USB ports both in the front and in the back. What the manufacturer probably doesn’t tell you is that these ports are not necessarily created equal. The front ports are typically on a different circuit from the rear-mounted ports (which are more than likely hard wired to the motherboard).
If you’re experiencing intermittent problems when using the front ports, try switching to a rear-mounted USB port instead. If you’re running short on USB ports (which is happening more and more because of all gear that can be connected via USB 1.1 or 2.0, including copy-protection devices like the iLok), you might try an AC-powered multi-port device or hub to provide enough power for all the connections. You can also add a PCI card with USB 2.0 ports quite reasonably.