Steps to show the problem:
1. create a widget project
2. write some code to load from a text file in resource, though the text file doesn't exists yet
3. compile the project successfully
4. add the needed text file in the resource (.qrc)
5. Rebuild/(Clean and build)
6. Run the project, the text file can't be opened
7. delete the build directory, build the project again, it works

BTW, Qt is good, Qt Creator is not so good