I'm using Omnisphere - if anyone is familiar with this instrument, maybe they can help ...
 
When I use one instance of Omnisphere inside X2, and load up new sounds on each channel, I start getting clicks and pops after about the 5th channel.   
If I use seperate instances of Omnisphere, same sounds but on different instances, I get no clicks /pops, even with 8 seperate Omnispheres running.
Something is causing the clicks/pops when in Multi mode - has anyone any idea, and is there something I can do to correct it?
 
Thanks

Ultrabra - how are the specs on your system? Do you have a relatively current set up or...?

PC spec:   relatively powerful
HP Z420, Intel Xenon E51620@ 3600MHz, 8GB RAM,  
Windows 7 Pro 64-bit
Soundcard in current use is Focusrite Saffire Pro 24 with latest software/drivers

are you routing each instrument in the multi to a different omnisphere output channel?? if you're running to the mains, you're likely clipping the signal.

Each of the 8 instruments in the multi goes to the same midi channel  (up to 8 sounds stacked on top of each other, though the overall levels though are OK, not even in the red ... )
 

i mean the audio outs in omnisphere.  in the multi mixer section where you have voices 1-8 each one has a midi in channel and an audio output bus.  make sure voice 1 is going to "out a" voice 2 to "out b" and so on, unless you want to combine a couple of them on the same channel. if they are all going to the same output bus you will clip inside the synth because all the voices stack up on the same audio out.

The other thing that I'd look at is if you're using an internal fx chain in omnisphere that the sequence might be causing some clipping and if the last fx in the chain is outputting below 0db then the master meters wouldn't show up in the red but it's still clipping somewhere in the chain. Lots of times this will happen with multiple delays.

Aha ... all outputs are set to A.   But that is normal for Omnisphere ...  
If there is clipping "inside the synth" as you put it - how can I check that, and prevent it?  
I actually just loaded a professional multi that I actually purchased, a stack of 6 voices, all output to A, and there is a lot of clicking/pops etc.   

Hrm. Kinda stumped. Try turning off all the master fx and see if the clicking is still there. I've paid for synth patches that were poorly programmed (i.e. clipped) before. I'll sleep on it too and maybe I'll get some ideas.

Is Omnisphere literally the only thing in the project ? Any fx or other synths that could be screwing with it ? Does it only happen in this particular project? Have you tried starting a fresh project with just Omnisphere in it loaded with the same Multi ?  What happens if you increase buffer size ? Will I ever stop asking questions ?........
 
Just throwing things out there......