Computer turns off with a click sound after about 30 seconds?

Hi,

I started to have this issue a few days back. When I switch on my acer netbook, everything is fine, it boots up; but about 35 seconds after switching it on (yes, I timed it and it happens after so long consistently!!!), it makes a clicking noise and just turns off!!!

I have already tried to flash the BIOS, but it did not help.

Here are my system specs:

model: Acer Aspire One 8.9 inch, ZG5

OS: Ubuntu 11.10

HDD: 160 GB

RAM: 1GB

Any help on what to do or where to look would be greatly appreciated!!!

Thanks.

Regards,

Ani.