Phew, after a long while, I figured out the cause of trouble.
Basically, my final attempt with strace, was
which produced the following output when opening the dialog box and after selecting a file, went onto repeat this line along with a couple others but mainly this:
Code:
open("/home/user_name/.config/QtProject.conf.lock", O_WRONLY|O_CREAT|O_EXCL|O_LARGEFILE|O_CLOEXEC, 0644) = -1 EEXIST (File exists)
open("/home/user_name/.config/QtProject.conf.lock", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 27
So, I just deleted the "QtProject.conf.lock" from ~/.config/
And that did it. Guess, it couldn't get a lock or something. But in anycase, thanks for all the help.