I am using OpenMP in my Visual Studio projects and currently thinking very seriously in changing to QT creator. (Doesn\'t Visual Studio suck?,I expect much more from Microsoft)<
In addition to esavard's answer, I found that I needed to add:
LIBS += -fopenmp
for the program to link properly. I'm running QT creator 2.0.1 with QT 4.7.0 on Ubuntu 10.10 (64 bit). Hope this helps anyone else running into the "undefined reference to 'GOMP_parallel_start'" type errors.