HELP!! urgent electrical problem.

[Bushbasher]

Ok, just did an oil change this morning and everything was good. Then thought I'd do a brake fluid flush so jacked up the front left to start there and once the wheel was off decided to turn the wheels hard left to make it easier to get at the nipple. Leaned in the window and turned the key and............ nothing.... except a steady beeping and the odometer flashing in time. WTF?? , I just fitted a new battery 2 weeks ago so it couldn't be that surely; but to be sure I hauled out the tester and checked the battery. 13.5V and the indicator in the battery is still green so the battery appears to be ok. All the fuses seem to be ok so I'm stumped . I pull out a spare battery and go to hook up the jumper leads and no sooner had I connected the negative lead than the thing came to life. DOUBLE WTF!!?? so out of curiosity I turned the key and the car started no problems, alternator charging normally at 14v according to the dash gauge. Disconnect the neg lead and turn the car off and nothing when you go to restart except the beeping. (15 times then it stops and the odo stops flashing too). I should also add that when I turn on the ignition the battery gauge doesn't move to read the charge at all and the dash lights immediately fade out as if the battery is cactus, except for the beeping. Connect only the neg lead to the battery from a second battery and we have normality. Obviously it has to be some kind of earth problem but buggered if I can work it out.

Can anyone shed some light on this and a fix cos I'm supposed to go to work at 4pm and I don't want to have to leave a dead car at home for the missus. We live 10km from town so if the missus has to go anywhere shr'll be stuffed.

Bushbasher