Final gathering dithering problem

[Leoung O'Young]

Sorry, resending this message, first message the attachment was too big.
Hi,

We are a little perplexed why we are getting this dithering in the dark 
areas using final gathering on some machines and not other
on a small rendering farm. We are using XSI 7.01, Mental Ray and Royal 
Render. I have attached the comparison

Any help will be appreciated.

Thanks,
Leoung
<<attachment: final gathering problem.jpg>>