Hi, I have observed something similar, although I don't have quite as stringent description as yours. But I have noticed that sometimes I get recompilation for no apparent reason. To be more precise I am editing in one project and another one that it depends on gets recompiled when I press build. When it is finished I can press build and it builds again.
At least that is what I think has been going on. This was on Win7 using MSVC2010 compiler and C::B nightly 10091, I believe.
I cannot reproduce easily, but I would like to confirm seeing what I think is reported in this thread.