Desktop file icon troubles

Got an application, and the corresponding .desktop file is this:

[Desktop Entry]
Version=1.5
Name=OpenTabletDriver
Comment=A cross-platform open-source tablet driver
Exec=otd-gui
Icon=/usr/local/share/pixmaps/otd.png
Terminal=false
Type=Application
Categories=Settings;
StartupNotify=true

This file is located in /usr/local/share/applications. If I click on the corresponding icon to launch the application, nothing happens. However, if I launch the .desktop file from the terminal (gtk-launch opentabletdriver.desktop), the application starts just fine.

What could be going wrong? :thinking: