I have had these issues for a while, only older nightlies work properly.
I just got an idea that somehow C::B now requires MinGW and GCC to be installed, whether you use it or not. I think I can confirm that suspicion. I had tried to edit away the GNU GCC entries from the default.conf file, but they kept coming back no matter what I did. So now I went and downloaded/installed MinGW with gcc etc., and installed it to C:\MinGW as is the default.
Then the error messages go away. C::B is also more responsive after I installed MinGW. The thing is that I am not going to use those tools.... and I think it should be allowed to use C::B without requiring MinGW installed. I have of course mingwm10.dll in the same dir as C::B, but there should be no need for anything more, and it used to be like that for years.
If I delete everything under C:\MinGW, the errors return.
I think there is now an expectation in C::B that gcc is installed, and I think it is a bug.