My Flashcard reader and USB OTG HD cannot live together at the same time

Once again, strange computer hardware setup drive me puzzled, and most of the time I just have to figure out the pattern and live with it.

For instance, when I have the flash card reader plug to my desktop computer, the system refuse to recognize the Look A6 OTG removal harddisk. But after I unplug it, the system can see the Flashcard reader again.

Also some strange issue when I plug the Firewire harddisk to my desktop computer when I already have the M-Audio Firewire Solo connected. I have to reboot, unplug the Firewire Solo in order to get the Firewire harddisk being recognized.