Optiplex 3240 USB issues

Hello,

Our company recently bought several Optiplex 3240 for a system control that uses multiple USB devices. However we are having some difficulty in getting the system to function as intended because when the the Optiplex is powered off for several hours it seems that it is not able to detect the devices connected to it. The strange part is that just powering off and then powering on the machine does not produce the same symptoms. The devices are connected to the machine with a USB hub. 

To get the system to recognize the devices we need to :

1. remove power from the hub
2. disconnect the usb from the hub
3. re apply power to the hub
4. connect usb to hub again

The problem seems to be in the Optiplex machine as this problem does not occur on a regular desktop. 

We already tried disabling deep sleep to fix the problem but to no avail.

I hope someone can help us with this as its proving a major setback.

With kind regards,