I just purchased an Alesis Multimix 16 firewire and am using SHS6 .I have a Gateway Dual core 2 gigs with 1 tb harddrive.Pent 4 processor using Windows 7 Ultimate.I downloaded the updated drivers for the Alesis and it was up and running fine,but had some popping and clicking during playback,which in the past i knew how to adjust for that.Now all hell has broke loose and i have nothing on Sonar, the meters on the Alesis all work fine but when i arm Sonar i have nothing,So i am clueless as to what happened,why at first it was just popping and clicking and now nothing!!! Any ideas anybody?

Go to Options>Audio and check all your settings.
Reboot the Alesis.

Thanks Gregy,i did do that and everything looked fine.I now have everything back but i am still getting that clicking and popping.I checked the latency,fooled with it a bit, but to no avail it just won't go away.I was wondering if i should go purchase a better firewire port as i am using the stock one that came with the comp.Any ideas? Also i am using the M-Audio 2496 sound card to use as playback,do you think that maybe that might be the problem?

That could be a problem.
Using 2 interfaces means you are using devices with different clock and they can't be synhed up.
Plus, you can't use ASIO driver mode when using 2 interfaces; you have to use either WDM or MME. I don't know if the Alesis has ASIO drivers (doubtful) but I know the M-Audio does.
You might change the number of buffers to se if the popping goes away.
And make sure no other programs are running while doing seerious recording. Many could cause pops and clicks, especially virus scans. 

See i thought that might be a problem running the M-Audio with the Alesis,two different clocks.The Alesis does have Asio but when i select it,the drop down for playback loses the M-Audio.How about trying the Asio4All download and see where that takes me,guess it couldnt hurt.Just kinda stumped at this point,using new interfaces sure can be a pain in the begining. This computer is dedicated for recording the only thing on it is Sonar and the Alesis and the M-Audio,no spyware or nothing not even the internet.

Yes, but not directly because of the 2496.
If you can select both devices, it means you are not using ASIO.
Both devices support ASIO, but ASIO forces you to choose only one.
In this driver mode, you would most likely get cleaner, low latency results.
I would lean toward using the MM exclusively, and taking the 2496 out of the chain.
Even then, if your latency is set too low, you may still get pops, especially with soft synth.
Play with latency between 5-10ms. Sometimes 1 or 2 ms can make a big difference.
As for the firewire port, the general consensus has been that a TI chipset is the way to go.
If your stock firewire chipset is not TI, that may be worth looking into.

Yea, i guess losing the 2496 is not what i wanted but if it has to go,it has to go.It's been a really good card,been using it for a few years now.I'll check into the T1 and see where this takes me.I've played with the Latency on both units and seems theres no happy ground for them to play nice together. Thanks Robert and Gregy for your time and expertise on this.Another couple minds always seems to find what one misses.

The Alesis does have Asio but when i select it,the drop down for playback loses the M-Audio.

ASIO mode only allows one soundcard at a time. Try WDM. 

So the problem was the fact that i didn't have a T1 chip set.I did learn a little trick that helped before i recieved my new card.For people using stock firewire ports,go to the device manager in your computer and change the IEEE 1394 bus host to" Legacy" drivers,makes a huge difference.