I believe Shady and I have the same problem.
I just updated to CMSF2 2.06, and now the game won't launch. I get the blue spinning for just a second, then...nothing.
This is the same problem I had with CMCW 2.05. After installing that patch, the game stopped working in the same way.
I am running CMBN, CMFI, CMBS, CMRT without the latest patches, and all work fine.
I surmise there is something in the coding for the PBEM system that is not compatible with my install (running up-to-date Win 10 on a Mac).
Yes, I put in a ticket for the original CMCW issue....a year ago (no resolution). Yes, I will put in a ticket for this issue.
This is very frustrating that I can't get updates and keep PBEMs with my friends.