USB 2 is effectively 60MB/S or should be, in reality I get 20-25MB/S tops from USB 2 drives.
Try an express card, return the regular PCI card. If you have an eSata try that, let me know if speeds are true to claims. It maybe a power allocation issue too, but I doubt it. MFGS. just lie about the performances of their boards and/or external devices. USB2 compliant = compatible, not performing at best USB2 speeds.