Is the fluid clean? If not replace the fluid. This may not be the Ultimate fix, but dirty fluid can cause problems as it's quality has depreciated like a new car does when you drive it off the lot. There are contaminants the build up and can affect flow or seals not to mention the heating/cooling properties of the fluid.
When the noise is happening, open the hood and have someone turn the wheel. Listen closley for the noise source. I would start at the pump.
If it is the pump, and the fluid change doesn't resolve it, it may have a fluid restriction causing the pump to overwork from a pressure problem, or the pump may be going bad. You can try adding a powersteering conditioner such a one made by Lucas. I have had it help on some and do nothing on others. But find the source first.
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Sunday, May 20th, 2007 AT 7:17 AM