Hi,
i have installed the Version X3b 64bit under Windows7 64. I own the Arturia Bundle "V-Collection3" , which some plugins are in the VST3 format (AnalogLab, Spark). I installed them as VST3 (in the same common folder than all of my other VST3 Plugins) but if X3 starts the first time after installing, the Arturia VST3 - plug-ins where scanned but they are not visible in the Browser after that first contact. Even then, when I fully put back all plug-ins an rescan the folders. Summary: No VST3 plug-in from Arturia works at the moment.
The next problem:
The u-he plug-ins DIVA, ACE and Podolski got out of tune to +2 semitones, after I pressed the start button in Sonar X3. Again: This problem exists only for the VST3 - versions. Interestingly u-he ZEBRA2 in the VST3 format works fine and does not have these problems.
The same behavior (with arturia and u-he) was already under X3a and does not seem solved in X3b.
Best regards from switzerland - and sorry for my bad english :-)
Frank