6800 ultra + 480W power supply. INSUFFICIENT

I took delivery today of a new Aopen Nvidia 6800 Ultra card. I also
installed my new Thermaltake 480W power supply into my Thermaltake 6000+
Xaser V Daimer case and tranferred my system to the new case. I also
connected the additional power lead to the 6800 ultra

Rest of system; athlon 2800+ 333FSB
512 MB corsair mem 2700
80G Maxtor HD
Abit NF7S Mainboard
Poineer DVD

Nothing overclocked,

On start-up I get a message saying that nvidia system monitor has detected
that the card is receiving insufficient power!!! and will run at a lower
speed to ensure stability.

This is very frustrating, I would have thought 480W would be more than
enough power - has anyone had similar issues?Could all the fans in the case
(5 of + PSU fan and CPU fan) cause a drain on the power??
How do I check the function of the PSU? Could it be faulty?
Does anyone own the Aopen version of the card? if so how have you found it?
I'm going to try downloading the latest drivers to see if that makes a
difference.

TIA

Toby