Latest Platinum version (2017.07) becomes unresponsive at a couple of specific times. Sometimes it doesn't start up and hangs at the splash screen. Other times is hangs during record or playback when something occurs to stop the operation such as reaching the end of the song or hitting the space bar. In all cases it will restart if I unplug my MIDI controller (AKAI MPK49). This did not start with 2017.07 but it has definitely gotten worse with this release. One out of every three or four times I stop playback or record Sonar hangs and I have to unplug/replug my keyboard then wait until Sonar asks if I want to reconnect it. This is really annoying. Anyone have any suggestions for resolving this weirdness?  

Regardless of latest Platinum 2017.07, it sounds like something has been going on for a while on your system.
 
I would start with the usual suspects, make sure your Akai and your StudioKonnekt have most recent driver updates and is your Windows 7 updated as well ? Then, check to see if your audio and midi settings can be adjusted to improve performance (you may have tried that already ?) Also, I wonder about only 8GB of Ram, depending on what you're trying to load up in your projects. Any other information you could provide will help the pro sleuths here find a resolution for you.
 
For example, I found with last month's Sonar update it was necessary for me to increase my midi playback buffers for a project I had been working on to fix some playback issues, it's always changing on my system, adjustments are needed depending on the intensity of the Sonar project I'm working on, or various Sonar updates or Windows updates that are going on.

Hey Noynekker - thanks for the response! Yes, it's been going on a long time and I've completely eliminated the freezes at least twice over the past couple of years but it keeps coming back! If I remember correctly, once by reinstalling Security Essentials and once by deactivating the HD audio on my machine - can't recall the other solutions. All the usual culprits have been checked. This time, I'm hoping for someone else to solve it and just hand me the answer :-) It's so time consuming and frustrating to track this stuff down...