No problems here - my external hard drive transfers data at between 30 and 40MBps.
Can you please provide some more information? Such as which device are you connecting?, has this device transferred at a higher speed while using another operating system or machine? Motherboard model (or the specific chipset/southbridge model if you know it)
If you are using an older USB device or plugging in a new device into an old USB port i.e. not USB 2.0 rated, the speed will be limited:
1.5 Megabits per second is the theoretical speed limit of USB 1.0
12 Megabits per second (1.5 Megabytes per second) is the theoretical speed limit of USB 1.1
Off topic but I'm looking forward to USB 3.0 becoming mainstream. It will have a theoretical transfer speed of approx 4.8Gbps (614MBps)!!