I've not done anything differently from yesterday to today, and I've tried multiple starts, under multiple situations and nothing. Anyone ever experience a random FSX just not deciding to open before?

Got any errors  boxes   shown  when you tried to start fsx , checked your event viewer  for any errors.  You could try a restore option to an earlier date if  no one else comes in with a better suggestion

Yep, and the problem was sweetfx. After removing all traces of it from the FSX folder that fixed the problem. Not saying that is the cause of your problem but it is one thing you could investigate.

If you are not getting past the "Splash Screen" there may be a problem with your

 

logbook. (It happens)!  Go to My Documents/Flight Simulator X Folder,

 

open it and find the logbook.bin file.  Re-name it so it's saved and then

 

start your Sim to see if it works.  You can always download a logbook

 

repair program to fix the original logbook.bin file.

So far so good, I tried renaming the logbook and seems to have solved my issues.