Hey Bimmer fans!!

I recently bought a BMW 525i of 1990. It was working fine until a few days back and suddenly one fine morning as I keyed in the ignition to start my Beast, any of the gauges won't show any activity.

The Temperature gauge, Fuel Gauge, Odometer, Engine speed Gauge as well as the economy gauge would'nt start to show any reading.

Steps I took:

# I checked all the fuse in the fuse box (1 - 29) and found that all of them are OK.
# I removed each and every fuse and then started putting in back, I put the fuse no. 1, 17 and 20 first because they correspond to the Instrument Cluster and the OnBoard Computer. But nothing showed up.
# Then I put the remaining, but as I put the fuse 10 and 11 my KMS gauge showed me the reading and the fuel gauge also turned up.
# Now I started my car and could see that the temperature gauge also started to move upwards, everything seemed to be working fine. But as I turned off the ignition, the display won't go off, so I unplugged the fuse 20 and then it switched off.

After that I tried again starting the car but nothing seems to be working, I did the whole exercise (as above) but nothing works now.

What could be the cause?

Any suggestions or advice would be great!!!