Please give some more details about your OS, driver version, ATI Stream (APP) SDK version... Do you have crossfire?

Hmm same here...haha looks like i posted on the main thread. But im running 5970 + 5850, 11.2 ccc and 2.2 stream with 25% load per poclbm instance. Win 7 64 bit here.

If you have more than 1 video card detected, Crossfire or not, in windows you will have high cpu usage. Try to start it with only 1 card plugged.

You all should probably read through a few of the other threads on this forum.

To get better performance, you should:

-Use Stream SDK 2.1.
-Use the display drivers from Catalyst 10-11.
-Turn off crossfire if possible.
-Use Linux. I've heard that people had problems running DiabloMiner in Ubuntu, so I might suggest Debian instead. There are guides for getting many miners up and running on different linux platforms if you're unfamiliar with how to use it. Look around on the forums to find them. Get ready to use the command line.

Kinda hard to do that with Cayman gpu supporting only 11.1 and later. Under linux there isnt voltage controll to reduce power consumption.

Any one with 2 cards & windows 7 32 also have this problem?

I have HD6870 & getting around 270Mhash/s after OC of core to 1038 & mem to 375, lowering mem clk reduced heat from 74C to 66C.
I do have the poclbm taking some cpu percentage & most time i see 20% in task manager.
I have 11.2 & 2.3 SDK.
However yesterday i find the preview of ati next driver version 11.4(not 11.3) with SDK 2.4 & installed it.
I see 2 difference mainly.
1. Before its always 99% GPU in MSI afterburner(only a straight line), now it floats from 92 to 99.
2.poclbm uses now 0 cpu, even though i am running with/without  -f1.

So, i think its not bad to try new version even though u have 5XXX series card.
Also, i still dont understand why all saying to use -w128 , as 6870 actually max work is 256 &  placing -w256 increases 2-4Mhash/s.

U can download the drive from here.
http://support.amd.com/us/kbarticles/Pages/Catalyst114earlypreview.aspx

Also, instead of express, go for custom & select only APP, driver, catalyst..only what u want, many r useless to mining, hydra...
Today, itself without a single reboot , i upgraded, downgraded, upgraded, downgraded.....from 11.2 to 11.4 & from 2.4-2.3-2.2-2.4....
Just go fro custom & don't install useless. U can verify ur SDK & ATI version using gpu caps viewer.
Hope this helps.

I'm also on Win7 64bit and seeing the same issue. Newest Catalyst drivers and Stream SDK.

Must have something to do with the 64bit windows. IIRC, I tried this on 32bit win7 and didn't have such problems. Maybe someone else could confirm if they're not having this issue on 32bit win7.

Luckily I have 4 cores.. But the rig is still consuming almost 100w more than it should :--/

I ran into the same problem, though it came to my attention in a different context.  My system is now:

Ubuntu 10.10
Radeon HD 5870
AMD Sempron 140

Uninstall every ati driver & sdk using some uinstallers like revo uninstaller.
Also never install sdk from stand alone adk package, instead install from driver package.
If you have 5000 series card, install 10.12 & 2.1 sdk.
If you have 6000 series card, install 11.2 & 2.3 APP.

You haven't mentioned what card you have, what OS & how many Mhash/s you getting.
Instead of going express install, go for custom install & install only these 4.
ATI display driver, ATI catalyst install manager, APP 2.3 or SDK 2.1 & VC++

exactly the same issue here!

rig:
intel 430 (one core)
X38 + 1GB DDR3
5970 + 6970 (3 GPU cores total)
drivers 11.2 with SPP and 11.4 beta, no extra SDK drivers are loaded 
win7 x86

when i am running one poclbm for the first GPU (whatever that be) cpu is at 1-4%
with the second poclbm, cpu goes 99%!!!!
with the third poclbm, cpu is devided for the 2 last poclbms (48%+48%)
i think, perhaps a bug with poclbm program?