yea, but this happened to me just 1 hour ago. What i did was this> ran bulldozer>very quickly just before its finished loading in i alt tab back to terrain builder and middle mouse click>then it will freeze for 5 sec approx>then you should see theblue bulldozer marker move>then i minimize TB and you should see buldozer fine and be able to use TB as well.
This fixed it for me, and also i realised that i had issues in layers.cfg because buldozer gave error message. So i fixed this, and now>no freeze.
i dont know if this is your issue, but anyway, you could try if you want. Good luck!