Mac Pro :: USB Or Peripherals - Screen Hub / Main Unit Intermittent Fault?

This is something I've been wondering for a long time. I seem to have a lot of screen-related issues with the Pros that I sit in front of in the main. Brightness controls going haywire displays not turning on, etc. There is also the odd attached USB device lockup, but I'd been putting this down to the devices themselves and the occasional, app-level instability of Leopard. More recently though, I've been seeing a pattern that's leading me to suspect the Pro's more than the peripherals. Is there a documented case of possible USB hub connection issues in (fully patched) 2008 Pros? The most frequent issue is monitors not behaving as expected when the system is booted until the monitors themselves are unplugged from power. There are also less frequent but present problems where iPods lock up, keyboards stop working, etc. I can't really abstract the problem down to an OS issue or a hardware issue, but the need for me to unplug the monitors seems to indicate that there is some sort of USB initialisation issue - as with the other minor problems I experience with other monitor-connected USB peripherals. Since I only use multimonitor environments as far as my Pros are concerned, all USB connections are usually made from the backs of the screens. So the big question is is this a screen USB hub fault, or a main-unit intermittent fault? All of the monitors I'm using have been to Applecare for one reason or another, although I'm not sure if they check everything in these repairs.

Can anyone else shed more light on this issue? It's pretty hard to replicate reliably and it's not been something I can go to Apple with any degree of certainty, yet the little minihoops I have with this problem (and oh so many other Apple issues, but that's by the by) irritate me immensely in comparison to my rock-solid, near-zero-such-issue, non-Apple environments which I also use daily.