A serviceable, Apple mouse and keyboard should be OK with any USB port, even the finicky ports on the newer PowerBook G4. Are these Apple mouse and keyboard? I'm guessing you get the 'needs more power' message when plugging those in, which would mean that: Your mouse and/or keyboard are defective (try a different one), or, using the external hub is what you have to do...
If a standard mouse or keyboard do not work, and you have tried a different set, maybe you can convince AppleCare to replace the logic board for this reason - if you are still in warranty.