Issue confirmed on Ubuntu 14.04 LTS.
running dia through the command: LIBOVERLAY_SCROLLBAR=0 dia
solves the issue.
As a complete workaround, you can edit the desktop entry file : /usr/share/applications/dia.desktop
Exec=env LIBOVERLAY_SCROLLBAR=0 dia %F
Issue confirmed on Ubuntu 14.04 LTS.
running dia through the command: SCROLLBAR= 0 dia
LIBOVERLAY_
solves the issue.
As a complete workaround, you can edit the desktop entry file : /usr/share/ applications/ dia.desktop
Exec=env LIBOVERLAY_ SCROLLBAR= 0 dia %F