A workaround that works for me under Unity is to double-click the title-bar - which causes the window to maximise. In its maximised state it has the three window operator buttons (close, minimise, restore/maximise). Hit restore and the window will pop back to its previous size, but now be resizable.
Prior to the workaround the title-bar only has two operator buttons (close, minimise), after maximising it acquires the third and resizability.
A workaround that works for me under Unity is to double-click the title-bar - which causes the window to maximise. In its maximised state it has the three window operator buttons (close, minimise, restore/maximise). Hit restore and the window will pop back to its previous size, but now be resizable.
Prior to the workaround the title-bar only has two operator buttons (close, minimise), after maximising it acquires the third and resizability.