I'm not sure if this is just coincidence, but immediately after installing the "E" upgrade, none of my NI soft synths will load into Sonar, but I get this error message " Failed to insert soft synth. The synth may not be properly installed." All of the synths are working fine in stand-alone mode.
 
I verified all of the dll's were in the proper directories, then reset and rescanned the VST's in Sonar. My EastWest Play (and other brand) soft synths are loading fine, it's just the NI product. When I select INSERT SOFT SYNTH, all of my NI synths are now found under DIRECTX/NI when they used to appear in the VST2 folder.
 
I'm going to call CAKEWALK support in the morning, but am trying to get a project finished tonight. If anyone has a suggestion, I'd appreciate it.

Try VST reset and rescan http://www.cakewalk.com/Support/Knowledge-Base/2007013315/SONAR-X3-Full-VST-Rescan-Recommended-for-Upgraders 

scook - Thanks for the quick reply. I had already tried the VST reset and rescan - made no difference.

guyprentice
 
I verified all of the dll's were in the proper directories, then reset and rescanned the VST's in Sonar. My EastWest Play (and other brand) soft synths are loading fine, it's just the NI product. When I select INSERT SOFT SYNTH, all of my NI synths are now found under DIRECTX/NI when they used to appear in the VST2 folder.
 

This was not part of the initial message I saw when I replied. Double check the VST scan path and make sure the NI VST versions are in the scan path. VST plug-ins won't be listed in the DirectX folders.

The VST scan path actually contains more folders than I use, as I consolidated all of the VSTs into one folder some time ago. But, that hasn't affected anything in the past, and shouldn't now.  I just went back in again and verified all of the dll files are still where they belong, and they are.
 
I can't figure out why Sonar is seeing the NI instruments as DirectX, and I'm sure that's where the problem lies, just can't figure out how it got that way, and what I need to do to fix it. The DirectX folder used to contain only the Cakewalk instruments (TTS-1, Cyclone, PSYN, and Roland GrooveSynth). Now, at the bottom of that list is an NI subfolder, which contains all of my NI instruments.
 
 

What OS?
What was the last version of SONAR that saw the NI VST plug-ins? I am guessing 32bit SONAR is being used.
Is SONAR running as administrator?
Which NI instruments are missing ex. Kontakt 5, Reaktor 5, Battery 3?
Do the stand alone versions still load?
 
DXi instruments are added to the registry during installation. They are not scanned by the VST scanner used by SONAR. DXi plug-ins can be installed anywhere on the PC.

Running Windows 7 -64 bit and SONAR X3-64
Sonar X3 Rev D worked - everything was running fine until the upgrade to "E"
All of my NI instruments are now loading into the DirectX folder. I have 10 of them, and all are probably pre-2009.
The stand-alones NI instruments work just fine.
SONAR is running as admin.

What does the Plug-in Manager report as the paths to NI DXi instruments? They can be found by running the Plug-in Manager, selecting the DirectX Instruments (DXi) category and the NI instruments. The full paths are reported at the bottom of the Plug-in Manager. It would be a first if these are VST dlls. While there check the VST excluded list.

While the NI instruments show up in the DirectX folder when you go to insert a soft synth, they don't appear anywhere in the plug-in manager - not DXi or VST.

Are you using the "Default All Plug-ins" layout?