QtCreator and old builds - why does it stay stuck with old config?

[been_1990]

Come and go QtCreator stays with old build configuration stuck, and no matter what I do it wont update itself.
Ex:

app.pro
app.cpp  -> Compiler error...
app.h
 
app.cpp -> Error fixed -> still same error ..
app.cpp -> Deleted -> still same error..
app.cpp -> Write any gibberish -> still same error

app.pro
app.cpp  -> Compiler error...
app.h

app.cpp -> Error fixed -> still same error ..
app.cpp -> Deleted -> still same error..
app.cpp -> Write any gibberish -> still same error

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No matter what I do to my code(that at some point produced an error), it still seems to use the old files of the project. If the error was with class EditMe(), even if I delete every mention to that class from the project, still the same old errors come out.
This keeps happening to me, with Win Vista, Win 7, Win 7 64bit.

This makes me go crazy every time. Must be the fifth time already.
Anyone know anything about this?