Right side USB port fails to function.

I just rescued a PowerBook G4 Aluminum 16" 1.67 GHz by cleaning the area to the below the right fan and to the left of the right speaker. I used WD-40 and 99% isopropyl alcohol. I also removed the logic board and the DC-in/Sound board.

I plugged in a Kingston 2 GB USB drive on the left side (featuring the modem and power jacks) and everything worked as expected. I unmounted the drive, and plugged it into the USB port on the right side (also featuring the Ethernet and DVI ports). There's no reaction from the laptop or the drive (no drive LED activity).

Anything else I should check and examine?

Thanks for reading!

I reseated that ribbon cable connecting that right-side USB board to the logic board. I thought it was unseated and needed some type of adjustment. I am now able to use the same USB drive that failed before. I'm embarrassed.