I check this problem on cbMakefileGen version: 0.3.12.3. C::B rev.5435.
I have no problem.
History:
I does loading my cbMakefileGen project (cbmakegen.cbp).
"Build target: default" was selected after loading. (I don't change it).
I does select from menu: Project / Generate Makefile
Ok. Makefile was created normally.
If you have problem, send me (on email) your project WITHOUT source files. (file .cbp only) I will try help you.
Good luck!