This just started recently. I have no detectable latency when using the pianos in Kontakt5 as VSTs, but I'm getting just enough to be a distraction (15-30ms) in stand alone mode. any ideas? Thank you.

Go up to the top bar in Kontakt and click on Options.
 
Go down through the settings on the left of those and look for something there. It may show as high as 4096 ms.
 
Also, if using Kontakt 4, on page 11 of the manual, there's a Latency Optimization slider to be aware of.
 
Lastly, check you're audio interface settings.
Sometimes jumping from a DAW or VST setting to stand alone may cause the latency setting to jump. I had this with Studio One & my Studio Live 16.4.2 mixer.
I couldn't figure out what happened - then I noticed that my 16.4.2 interface setting had jumped to 4096ms - ouch!

Go into the Audio tab on the Options dialog in Kontakt. What does it show for "Latency"?
 
You're going to want to set the ASIO buffer as low as possible, preferably 64 or even 32 if your computer can handle it and your interface driver offers it as an option. That'll get you under 4ms, adequate for realtime piano.
 
As for why the latency is greater in standalone, that's a mystery. Assuming you're using ASIO, buffer size should be the same whether standalone or hosted as a VSTi.

twanghang
This just started recently. I have no detectable latency when using the pianos in Kontakt5 as VSTs, but I'm getting just enough to be a distraction (15-30ms) in stand alone mode. any ideas? Thank you.

 
Latency has but two sources:

• Your audio interface's buffer size
• Any latent plugins (in this case it would be convolution reverb)

Go into the piano library's EFX section and find the Convolution Reverb.  
Make sure its Latency setting is at "0 Latency"
 
Make sure Kontakt standalone is set the ASIO... and that the proper driver is selected.
If you have Cubase installed, it will install a "generic ASIO driver" which may have bumped the proper driver out of place.  This is very common... and would explain the unexpected higher latency.  
The generic ASIO driver can be removed via the registry.
 

The stand-alone versions may well install with WDM driver mode, rather than ASIO.  I always run through each of my Komplete components in stand-alone mode, to make sure that are set to my ASIO drivers of my audio interface.
 
Bob Bone
 

Man, I LOVE the responsiveness of the users in this group! Makes me so glad I went with Sonar. Indeed, the driver had switched somehow to WASAPI from ASIO and was showing a round trip latency of 20ms. When I switched it back to ASIO it shrank to 5ms. Thanks to all who responded!

I am happy that it was that easy.  Glad you are back in business :)
 
Bob Bone