thanks for following up.

If you don't have a AppleIRController.kext on your hard drive, you're 
lacking the driver for the Apple Remote.

Quick try to fix the problem could then probably be to just copy the 
driver bundle over from another OS X install, or use Pacifist and 
search through the Mac OS X Installation CD / DVDs to extract the 
required files.

That still wouldn't explain why your IR receiver does not show up in 
System Profiler, though. Driver installed or not - the hardware 
should always show up there. So, yes, having your Mac checked at an 
Apple Store is probably a good idea.

Good luck!

Best regards, 
Felix