bousozoku said:
It may be the case that it's not working at the full potential of USB 2.0.
Some things work at full-speed (12 Mbps) and others at hi-speed (480 Mbps) so if it only says USB 2.0, you can't really tell what you're getting.
Yes, you can. Open up Apple System Profiler, go to the USB section, and it will list the speed of every USB device on your computer.
1.5 is 'Low' speed, used by keyboards and other ultra-low-bandwidth devices, 12 is 'Full' speed, and used by fast USB 1.1 devices like mice, scanners, printers. 480 is 'High' speed, and is the USB 2.0 speed that is for hard drives, video cameras, fast scanners, etc.
Also make sure that if you have it plugged in through a hub that the HUB is USB 2.0 'High Speed' compliant. An older USB 1.1 hub will only allow 12 Mb/s max, even when plugged into a USB 2.0 port on the computer.
Finally, as kernow said, reformatting as the Mac-only format 'HFS+' could make it much faster. I've had some drives formatted as FAT (MS-DOS format,) that were just as fast as when formatted as HFS+, others that were only 10% the speed of HFS when formatted as FAT. (So formatted as Mac-only made them 10 times faster.)
P.S., also as bousozoku says, some devices claim 'USB 2.0' compatibility, but still only run at the USB 1.1's 'Full' speed of 12 Mb/s. You have to make sure it says USB 2.0 'High Speed' to be sure it will run at the 480 Mb/s speed.
Also, 1.5/12/480 is the INTERFACE speed, not necessarily the speed of the device. Most flash drives can't get anywhere near 480 Mb/s in actual use, but most modern ones CAN exceed 12 Mb/s.