I think stardocks away for the weekend, so besides their general support FAQs or a direct reply from them. I have some questions/tips for you to try out in the mean time.
-When you uninstalled did you also manually delete all the custom races you had already from the saved games folder?
If the steam cloud sync is on you may need to turn it off so it dosnt just bring them all back.
-Also does it freeze when you make a brand new race from scratch not just a copy?
If so, have you tried making a race that dosnt have any custom assets, such as portraits, ships etc.
-Do you have any custom races in as AI opponents?
- Have you tried disabling all mods
Reason i ask is, because if you use races made from earlier versions of the game, like the 1.0 (maybe 1.1) or earlier. There was a update made to the custom races that made alot of them incompatible or corrupted.Which is now fixed and shouldn't happen again but the races braking was necessary for the fix before the workshop come out.
Ruling out all the normal things which im sure you have looked at like minim requirements, graphics updates and things like that.
A test situation would be making a game with mods disabled, no custom races for the AI, and a brand new custom race not using any old custom race files or your own custom art. (the art shouldn't matter but its just a test). Then if that works, from there slowly add things back into the game until you get a freeze again, hopefully allowing you to eliminate and find the route cause.
oh, and for good measure try a small map with minimal opponents to rule out a memory issues.
Hope that helps for now? im sure others or stardock will have a better response but didnt want to keep you wanting