Can I replace whatever controls the bluetooth in my Imac?

I have a G5 iMac and after 3 years, the bluetooth connection to a wireless keyboard and mouse constantly cuts in and out. (works for 3 minutes, then won't, then will, etc.)

I've tried the same mouse and keyboard with my macbook and they both work fine with no dropouts.
I've checked for any updates to airport and there are none.
I've tried searching here and at several other forums...I tried deleting some file people suggested and that didn't work....in short I've tried everything I could and nothing has worked.

The only think I can think of is that the bluetooth "controller" or whatever is the engine for the bluetooth in the Imac is just plain bad. The problem is that I don't know exactly what or where it is, or if it is even replaceable?

I have to fix this problem soon because as you might guess, it is really driving me and my wife nuts. Thanks for any help.

 

hmm...2 really good suggestions, thanks
I guess one of those BT dongles would work fine, I wasn't even aware of them...I think I'll buy one tomorrow.

But still...this got me to thinking about my original question...is it actually possible to replace the card or controller inside the computer?