I tried loading the same demo project and adding the same two plug-ins to the same track as in your video demo. Trying the same thing with a variety of audio interface latency settings, from 2ms up to 100ms, I could not get the freeze as in your video. I could even do the soloing/muting rapidly in succession (alomst double click speeds) with no issues on the audio or video sides.
Note that I am using SONAR X2 Producer x64, not Studio, though I wouldn't think that should matter in this context. My system is far from state-of-the-art, with an Intel Core 2 Duo E6600, 4 GB of RAM, an ATI Radeon HD 2400 series graphics adapter, and Windows 7 Professional x64. Audio interface is an E-MU 1820M (that's a PCI interface).
One thing I wonder about is if there may be some tuning parameters that are different, be it in SONAR or Windows. While I didn't do anything special in tuning X2, I may have done some tuning in past versions of SONAR, and it's possible that may have gotten carried forward by the upgrade. I don't think I do anything special with respect to Windows 7 tuning (I just checked my tuning settings and I am optimized for programs rather than background services in the processor section and it looks like most of the display enhancements are turned on in that section).
Rick