As I've stated in another forum, with the proper Samsung cable, I have this problem with my laptop. However, if I use a slower speed USB1.1 port like that on the keyboard or LCD monitor I use with my laptop, I have no problems.
Interestingly, with the same Samsung cable, if I plug my phone into the USB port on my Sony car stereo, I have no problem browsing the music on the radio. So, I'm sure as can be, the issue isn't with the cable. Now, it's possible that the USB ports on my laptop just don't put out enough current, but I don't think that is the problem either.
If you don't have USB ports that will work, the easier method to move files back and forth to the phone (and don't be unplugging your microSD card each time - that connection wasn't designed for many connect/disconnect cycles), is to use FTP. Install SwiFTP from the market onto the phone, and Filezilla from the web onto your computer, and transfer files via FTP/WiFi.
Alternatively, install MyPhoneExplorer from the market onto your phone, and also from the web, a program with the same name onto your PC. Open up the firewall on your PC so it can find the phone.