This is a weird problem...

[blacklabel]

Evening all, I have experienced a problem with my trusty old 98 AU Futura that has never happened before and has me scratching my head-so any advice would be grateful.

I got in my car yesterday and drove to pick up a friend for work.
We jumped in and I went to start the car.Nothing...and I mean nothing! No cluster lights,warning lights or anything,no starter,-nothing.I turned the key back to off position and tried again.Nothing.And tried again-this time,no starter-but the whole dash was lit up like a xmas tree-including the word "base error" in the lcd display area.Still wouldn't start though.So I shifted the gear stick out of park and up and down the gears and back to Park a few times.Finally after doing this 4-5 times the normal cluster display was present and she started first pop.The stereo "error" code was also showing and I had to re-enter it.
I thought it must have been a loose battery terminal connection,and checked and tightened a firm but not very tight positive terminal.
Sweet as for rest of day and today-until I got in to go home from work-and exactly the same thing again.No power,no dash display,no starter!
Again,after many in and out of "park" jiggles with the gearstick it went back to normal and started first pop,as she always has for 3 years!

One friend has suggested it could be something to do with the immobiliser malfunctioning.Another reckons it's the electronics to do with being in "park" for starting.
Has anyone had this happen to them?
It's got me stumped,and it's real annoying.
Thanks.