Computer USB transfer speed

Just rephrasing my previous question on SIOC and USB transfer speeds.

I have 3 USB DC servo motor cards running 17 gauges total (modified real engine gauges and one flap gauge).

Each IO board USB cable runs to a dedicated powered USB hub.

My main computer is running FS9 with Wideview networked to 7 computers for outside visuals. This main computer also has the USB "plug and play" rudder pedals, and associated Bodnar Board connection (USB) to operate flight controls, landing gear etc.

So basically I have two powered USB hubs with about 8 cables running to there comsumers, and a couple of USB inputs connected directly to the computer.

Normally....everything runs smooth...no lag in the engine gauges etc etc.

Occasionally....and I mean occasionally....I will fire up the system and the all engine gauges with the exception of a couple will lag...or stick for up to 8 seconds before the 'get the input' from the computer and operate.

If I don't reset the computer, they will remain like this.

Now...i have no antivirus software on this machine (as I do not connect it to the internet) as my initial opinion was it was running a scan of some sort....but it almost seems to me that something is running inside the computer to slow things down .... occasionally.

Last night I shut down and fired up the computer half a dozen times and every time the gauges worked perfectly!

I am using window XP if that helps??

Any thoughts?