[CMake] Problem with NMake generator after upgrade from 2.4.6 to 2.6.3

[Dieter Oberkofler]

After having upgraded CMake from 2.4.6 to 2.6.3 I received the following
warning

==========
...
-- The C compiler identification is MSVC
-- The CXX compiler identification is MSVC
CMake Warning at C:/Program Files/CMake
2.6/share/cmake-2.6/Modules/Platform/Windows-cl.cmake:32 (ENABLE_LANGUAGE):
  To use the NMake generator, cmake must be run from a shell that can use
the
  compiler cl from the command line.  This environment does not contain
  INCLUDE, LIB, or LIBPATH, and these must be set for the cl compiler to
  work.
Call Stack (most recent call first):
  C:/Program Files/CMake
2.6/share/cmake-2.6/Modules/CMakeCInformation.cmake:39 (INCLUDE)
...
==========

and CMake aborts.
 
The CMakeList.txt files and the environment did not change at all and the
compiler (cl.exe) can be executed from the same command line I'm executing
cmake from.
 
Any help would be appreciated.
 
-Dieter