We have found that with certain GPU's on the Chrome browser, when a Gliffy diagram is exported, certain shapes, such as BPMN, will appear as black squares.
The user should attempt to first make sure their graphics driver is up to date. If this does not resolve the problem, the user should turn off Canvas 2D GPU acceleration by typing in chrome://flags in the chrome url address bar and setting the following:
Disable accelerated 2D canvas Mac, Windows, Linux, Chrome OS, Android
Disable the use of the GPU to perform 2d canvas rendering and instead uses software rendering.