System hang when usb device plug in

Hi All I've buliding up two computer in approx. one month ago and found both of them have same usb problem The system is hanging up when I plug in any usb device (when I plug in such as usb pen disk or card reader it just fine, but it hangs when I opened "my computer" and it became no response, in the meantime I can still access to the internet or other programs except "my computer" ) But all devices works fine if I boot the pc with the devices plug in It hangs only when I plug in the device when the windows is running my config as below: PC 1: CPU: AMD PHENOM II X2 HDZ550WFGI 550 CPU [AM3] BOX [Black Edition] MB: GIGABYTE GA-MA785GT-UD3H/AM3 AMD 785G,DDR-III M/B Display: Sapphire HD4830 Golden PCI-E 512MB Ram: Super Talent DDR3 1600 2G Ram WA160UB2G x 2 Power Supply: ANTEC EA500 EARTHWATTS 500W OS: Windows Vista Business 32bit PC 2: CPU: AMD PHENOM II X2 545 MB: MSI 770-C45 AMD 770,DDR3, ATX M/B Display: Sapphire HD4830 Golden PCI-E 512MB Ram: Super Talent DDR3 1600 2G Ram WA160UB2G x 2 Power Supply: ANTEC EA500 EARTHWATTS 500W OS: Windows Vista Ultimate 32bit Do any one have an idea on how to fix this problem? Thanks for the help.