Stop / Shutdown Windows then disconnect at USB
If you are constantly plugging-in and pulling out USB connections, Windows (assuming you've this O / S) loses the driver(s) for the USB connectors. Because you've "interrupted the service" by disconnecting / stopping a 'running command' to a USB controlled device without using the disconnect tool / stop device button-
" Safely Remove Hardware ". When USB controlled devices became available their best functionality over PS/2 devices (keyboard & mouse) was that to begin using the device you did not have to restart the computer to begin using the item, the catch cry was "true plug and play"
You can 'Update' all your USB drivers again by;
<- left click on "Start"
<- left click on "Run"
<- in the dialogue box type "devmgmt.msc" (Win XP pro)
<- left click on the
+ adjacent to "Universal Serial Bus controllers" to open / display the tree
<- left click on a USB controller where there is no device attached
<- left click on "Update Driver" and follow the directions to one-by-one re-establish each individual USB socket
<- then restart your computer and so long as you don't yank out the device before disconnecting it or shutting down Windows all devices should have P-n-P functionality.
If you need more connections buy a powered HUB?
Hope this helps