bapu
That right there tells me a change was made to VST3 handling in Kingston which had an impact on VST2.

Could have been a change to VST2 handling which was not required for VST3?

Dear scook,
   My hat is off to you sir!  Your information has resolved my problems with the synths Iris 2 and Novation Bass Station.
   I realized that I have been loading the VST 2 version of Iris.  I changed that to the VST 3 version.
 
   What is the downside (if any) of not using the 64 bit precision engine?
 
   Thanks again for your help and also to Cakewalk for quickly alerting me to your forum post.  What a wonderful group of people!

There is some question whether running the 64bit DPE all the time provides any benefit. I usually have it disabled and rely on the bounce and export dialogs to control when it is used. Even then, I am not sure what I do benefits from having it enabled. I would suggest testing and see if it makes a difference in your case.

Yep your right!
My sylenth the same after coming across this thread, thanks guys

Ans Scook, I did disable the double precision engine and sylenth is okay again!

scook
So far disabling the 64bit Double Precision Engine in Preference > Audio > Driver Settings has solved this for several other synths. Give it a try.
 
When it came to Iris2, I could only make it fail using the VST2 format. The VST3 was unaffected by the 64bit DPE setting.

You sir are genius! I owe you a coke! Thank you so much!

Well, I guess I wouldn't have been able to repro this anyway, since I have double-precision setting turned off.
 
Great that a simple workaround exists.

Enigmatic
 
You sir are genius! I owe you a coke! Thank you so much!

You own Dan Date from CW the Coke. It was his idea. I just tested it and spread the word when it worked for me.

ok ... will try this for syleenth.. is this a fix for 32bit or x64 versio??

I only have 64bit SONAR installed. I do not recall any report specifically mentioning 32bit SONAR or details about the plug-ins other than the plug-in name.