Hi guys, thanks again for all the helpful suggestions. So I've tried alternative USB ports, disabled all other audio drivers, disabled the wifi, run through Windows dskchk and memchk, Overclocked the PC to run at 4.2 with no cool n quiet or CPU overdrive or boost, removed my USB devices other than keyboard and mouse and disabled them in device manager and still no joy!
 
I'm currently installing Pro Tools first to check that, if that runs okay I guess my next step would be to try uninstall Cakewalk then re-install it. If I was going to do this what's the best way to install fresh whilst getting the elements I've paid for from Cakewalk Sonar but installing the Bandlab variant? If I have to re-install Cakewalk I shall probably restore Windows at the same time just to check that as well.
 
Thanks again guys!

Were the alternate USB ports USB 2? You didn't seem to specify. Some/many newer motherboards have zero USB 2 ports, and you want to make SURE you know which ports are of what type.
 
This certainly is likely to be something local to your system, 
 
Bob Bone.

Hey Bob, they are indeed all USB 2 ports :(
 
I have though found that Cakewalk is the problem or the efficiency/compatibility with my system right now is. Installed Pro Tools First and straight away created 5 separate instances of Hybrid II, midi keys in with the buffer set to 64 and no pops, clicks or anything. I've already reset the preferences to default in Cakewalk and still no joy so I'm guessing it's a compatibility issue which is really annoying. I've just spent 18 months learning it regardless of the pops and drops :(
 
Anyone got any last minute advise on this now we know it's software related?
 
Thanks to you all for the help and support

Other thing to note is that Pro Tools First barely touches the processor in comparison to Cakewalk my system usage in Pro Tools sits around 2% when playing back 6 instances of Hybrid whilst it's nearer 50% in Cakewalk.