ld.exe: cannot find -lQtCore

Hi,

I am working on an open source code. When compiling, building and running in debug mode, the project works however putting the project in release mode, I get the following error at the make stage:

c:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../../mingw32/bin/ld.exe: cannot find -lQtCore
collect2: ld returned 1 exit status
mingw32-make.exe[2]: *** [..\lib_win32\QtAV1.dll] Error 1
mingw32-make.exe[1]: *** [release] Error 2
mingw32-make.exe: *** [sub-src-libQtAV-pro-make_default-ordered] Error 2
08:49:43: The process "C:\QtSDK\mingw\bin\mingw32-make.exe" exited with code 2.
Error while building project QtAV (target: Desktop)
When executing build step 'Make'

Please let me know what am I missing.

Thanks very much.
Ibra

PS: I have extensively used google searching to try and resolve this issue on my own but couldn't find the answer.

Have you deleted your build directory and run a complete rebuild?
Have you recently added/removed Qt versions?

What is the actual ld command that was executed to produce the error message. I probably has the wrong (or no) library search path.