Bluetooth Not Available


I have an IMac G5, running OS X.4.2. I have a bluetooth keyboard and mouse. The Bluetooth icon in the upper right part of the screen has a crooked line through it and when I click on it, it says "Bluetooth not available". I have tried zapping pram, also Apple, Option , O, F. I have removed USB peripherals, all to no avail. The System Preferences do not indicate the presence of bluetooth at all.
This has been happening on and off (at first I thought it was a conflict with my Dymo Labelwriter USB connection), but now it seems there is no solution. Any ideas?
I'm having same problem with powerbook G4 1GHz. All since I performed software update. Have tried everything. Now even wiped hard drive and reinstalled 10.2.8 to see if that would help. Still no joy. Since then my battery life has dropped from 2hr on full charge to 20 mins!!! Please please please has anyone got any ideas?