Help - sound cuts out when I hit bumps

[mobilejo]

My 2001 X5 without DSP and with mk2 nav has the sound cut out when I hit hard bumps. As soon as I skip to the nect track or switch sound source (FM -> CD or vice versa) it usually comes back. Although on one occassion it didn't come back and when turned the ignition off the dash said "tail light fault" "brake light fault" and "check number plate light". When I turned it back on the sound was back.

My thoughts are a possible earth problem (as the lights were affected on that one occasion) which is only highlighted when hitting the bump and is fine again straight after.

Anyone know where the amp/lights are earthed? Or have any other suggestions?

Thanks