I am using Intel D945 GCNL board. When using 3G USB data card in one of the USB port, other USB ports becomes nearly functionless i.e sometimes working and sometimes not. specially the front USB becomes workless.They do not read any pendrive or other equipments. And when 3G data card is plug out, the ports works normal. I have checked the voltages in the USB ports in both conditions i.e. when the 3G card plug in and plug out. In both cases there is no major difference. Only a voltage drop of 0.01 V is observed when 3G data card in plug in. If there is a solution please send the solution to akd260671@gmail.
I've seen this problem myself on a couple of different motherboards. On one, when I plugged in a USB drive, the USB wireless network adapter that was plugged into the adjacent port would stop working. Unplug the USB drive and suddenly the network would connect again.
I did some experimenting and found that I could repeat the symptoms exactly by moving the network adapter to another pair of USB ports. When I tried to use the adjacent port for another USB drive the network again stopped working. The problem was repeatable on each pair of USB ports that I tried. However, when I made sure that the two devices were connected to a different pair of USB ports(only 1 of each pair plugged in) then everything worked fine. The 2 motherboards which exhibitted this were both AMD boards, one was a 760G chipset and the other was a 785G chipset. I still have the latter board (an ASUS M4A785G-M) installed in a spare computer.