Subject says it all really.

I have seen cars with the same problem bt never on mine until now.

Anyone know how to cure it?

check no bulbs are out, if none are out possibly relay seen better days. Normally caused by a bulb out, not necessarily (sp) indicator bulb either

Have you done any wiring lately and do you have any modifications which needed electrical work at the time.

Reason I ask is that with my previous car I tried fitting a rear top brake light and had to wire it to one of the exiting brake light wires. This caused the indicators to flash rapidly. I had to remove the top brake light.

It might be some wiring is touching metal somewhere.

Just and idea though. could be many other reason`s though

As scott said, this is usually a symptom of a blown bulb... Check around the car and you will find one blown no doubt.