Project is not built after adding new class

(1) Create a new project (for example, GUI).
(2) Simply build the project.
(3) Right click on the project and select add new.
(4) Select C++ class, click ok, give it a name, and finish the wizard with default values.
(5) Try to build the project.
Result: The project is not built with the following error message:

Failure to read QMAKESPEC conf file c:/../SCM/Internal/qt/qt/mkspecs/win32-msvc2008\qmake.conf.
MAKEFILE_GENERATOR variable not set as a result of parsing : C:/QtCreator/qtcreator-2.0.0beta/untitled15/untitled15.pro. Possibly qmake was not able to find files included using "include(..)" - enable qmake debugging to investigate more.
command failed with exit code 3
Exited with code 2.
Error while building project untitled15 (target: Desktop)
When executing build step 'Make'

Note: If I skip step 2 this problem does not happen. (Repeated many times to make sure.)