I had a PDA mounted on the dash of my car that exhibited extreme slowness.
I finally discovered it was due to the IR port trying to communicate with
the sun. I tried to turn it off in the software, but ultimately covered
over the port on the top of the PDA with a small piece of black electrical
tape. Problem solved. I initially discovered this was the problem when I
threw my hat over the unit in disgust and discovered that the perforance
immediatly recovered.

You can usually see the port flashig if you point it at a webcam and look at
the resulting video on your computer screen. The webcam sensors are usually
sensitive to IR.

John