USB hub causing a blinking amber power light

Recently I have had a problem with my computer turning off for no reason or not starting up after being shut down.
Whenever I would try to start it back up, the power light would blink amber.

For some reason I just happened to knock out the USB cable for a cheap i-rocks USB hub/media card reader. The computer spang to life as soon as the hub came unplugged.

My question is, why would the USB Hub cause the computer not to start? It's a powered hub, so could it be drawing too much power during start up?

I really need a hub, not the media card reader, the computer has one built in.

Thanks for your help

Oh, this is on a XPS400