www.makemkv.com

What the crap is going on with this.
I'm running windows 7 64bit and I've been running a registered copy of Makemkv for awhile now. Today I get the dreaded "Application failed to initialize" error
I've uninstalled the application from control panel
Deleted all references to Makemkv in the registry
Deleted the Makemkv folder under the user profile
Emptied the recycle bin
Rebooted
Installed 1.8.9

And I still get the "Application failed to initialize" error

This is getting ridiculous

While it seems you've followed all the steps, did you make sure the C:\Program Files (x86)\MakeMKV program directory was empty?

One of the things that goes wacky on Windows is that, if you log in as an administrator to install something, but later use a different user name (also an admin) to make changes, some things can't be overwritten. The same thing can happen under Linux or OSX, but Windows users don't expect it. Heck, I forget it most of the time!

Mixed versions of files is the biggest cause of the "failed to initialize".

However, there CAN be others. The system event viewer can often help you localize things a bit, since it is SUPPOSED to record WHY things couldn't initialize.

Control Panel -> Administrative Tools -> Event Viewer, or "eventvwr.msc /s" if you want to use the Start -> Run menu.

Not sure if the OP found their answer yet, but i found my ISP provided anti-virus (F-Secure) was blocking a needed file.

worth a try; for me, I navigated to c:\program files\makemkv and tried to start makemkvcon.exe - when the AV program states it's blocked, unblock it. It will still fail to start, but then you can start MakeMKV normally.

YMMV