It's one thing to post a fix, and it's another to explain how I arrived at the fix. As a web developer (and very very long time Mac user), my life is debugging so I have a few more tools to pull from. Hopefully, advanced users will be able to follow my logic to arrive at this fix. You can skip past the following to get the fix, but this explanation may help you to troubleshoot not just Maschine but other apps. I'm not a magician, and I do not pretend to be one, and you too with some practice and time can start learning to troubleshoot computer programs.
So recently Maschine stopped working randomly. Having a fair amount of technical prowess I wasn't too worried. I went to my Activity Monitor. For those not familiar, OS X comes with an application bundled in every install called "Activity Monitor," in your applications/utilities folder. Activity Monitor is a GUI (Graphical User Interface) to several UNIX applications that can be accessed in the OS X's terminal. These applications allow you monitor memory / CPU / network usage. As a debugging tool, it's a must as you can see if an activity is slowing your computer down by overly utilizing CPU cycles, ram or bandwidth and force quit tasks that can't be accessed by the normal force quick menu.
I fired up activity monitor and located Maschine in the list, and double clicked it to get more info about the process and to see which files it recently accessed. Even to me, most of what appears in the log files are a garbled mess of esoteric computer-speak, but I also know that there's relevant info in these logs. Fortunately, files accessed logs are straightforward. In the log, the last files accessed were plist files pertaining to it's freeze state.
As an OS X veteran, I knew offhand a few things: plist files are preference files that sometimes get corrupted. They usually can be deleted without any repercussions as the application in question will regenerate these (worst is some settings may be lost) and more importantly that the .saved has to do with OS X's ability to relaunch applications to their last known state. As a rule, Freeze states are pretty much always ok to delete, in fact occasionally you need to dump a corrupt freeze state. This is common practice in iOS when users double tap the home button and swipe up to close a frozen app as iOS doesn't by default "quit" apps, but places them into freeze states. Deleting a freeze-state simply forces the application in question to fully relaunch.
I started by dumping the Saved Application state, always an import first step in modern OS X debugging but it didn't work. After talking to my buddy Justin, he mentioned that the time Maschine stopped working when he changed plugins. So I had a hunch and decided to take a memory sample in the activity monitor. Memory samples allow you to peek inside to what your application is doing and what information is being accessed at that moment in time. Remember how I said even I don't understand much of what's in a log file? This is one of those times. We know that the application is hanging, so something is causing it to hang, and we can bet that the problem can be "seen" as the program will likely try to access something repeatedly, or we may see the last item the application tried to read before stalling out.
(the screen caps are clickable for legibility)
Note that during the hang, the memory sample is calling PSP echo, which is a popular audio plugin. Maschine like many audio applications runs an initial plugin scan to make sure all the plugins installed are compatible and if they aren't they're blacklisted so they will not crash the host application. This scan usually is run only if the application detects a change such as a new plugin install. This sometimes fails and causes an application to crash. Apple's Logic has the ability to detect failed launches and thus rescans its plugins on a failed launch (a somewhat recent innovation with Logic 8 or 9). Maschine is a little more limited, doesn't have this ability, so it's up to the user to manually reset the approved plugin cache. While I couldn't find the Maschine 2 location for plugins list, I found the following article MASCHINE Crashes at Startup (OS X) which pointed me in the right direction.
How to fix
Step 1: Go to the following location on your computer:
Users/[your user name]/Library/Application Support/Maschine 2/
Note: You may need to enable your user library folder visibility if you have not done so already.
Step 2: Drag all the files into your trash.
Step 3: Relaunch application.
With any luck, you should see something like the message above. Happy Beat Making and troubleshooting! Remember, the activity monitor is one of the most critical tools in a power user's bag of tricks. OS X is big and complex, but almost nothing is done behind closed doors, this means there's nearly always a way to get to the root of a problem.