HELP! I'm banding!

[Mask_of_Dionysus]

bonjour, hello, yassou, yadda yadda yabadabadoo

OK, I'm at the point where I'm thinking flying to the Canadian Tundra is a wonderful idea /cry.gif' class='bbc_emoticon' alt=':(' />

The problem. It's simple really, but can't figure it out - I've never had such a problem with gradients.

I'm working on the background for a client's 'announcment card'. The background is a two-colour gradient + black. At first I got a moire pattern, and got rid of it. NOW I'm getting banding and I CAN'T GET RID OF IT ! /shocking.gif' class='bbc_emoticon' alt='(ack)' />
I've tried all the usual things to get rid of unwanted patterns with no luck - I'm at my wit's end.

This client is increadibly picky so it must look absolutely FABU(lous), dahling. /bad.gif' class='bbc_emoticon' alt=':puke:' />

Any help, advice would be greatly appreciated

Dio (Air Nunavit anyone?)