Hiya,
I had exactly the same problem. It is a problem with one of the mods. I went through them all by dragging the mod folder to the desktop, then making a ne folder in the steamapps directory.
Then i put back 10 mods per time (alphabeically so i knew where i was) and started the program.
Eventually i had 4 mods, all related that were the cause of the problem.
In my case it was Ricks Walkers zombie mods. so if you have them try that first.
This worked for me and i havent had a problem since.
ciao