QT Creator drop down menu empty

Hello all,

I recently installed QT5 in my ubuntu 16 machine and I am experiencing the following issue with QT Creator 2.7.0.
I can see the menu bar and each voice is correctly displayed, but whenever I click on one of them the specific drop down menu is completely blank.
If I click on one line I can see the menu is working but all the drop down menu is all gray without any voice correctly displayed.

I was wondering if someone had the same issue as me and what has been the workaround.

Many thanks in advance.