Currently Dynamic Web TWAIN Plug-in for Mac doesn’t support Safari 5.0 when it’s run in 64-bit mode (5.1 or above is ok) . Therefore you need to run Safari 5.0 in 32-bit in order to use Dynamic Web TWAIN Plug-in for Mac. To do this, please follow the below steps:
Right click on the Safari icon in the Dock. In the pop up menu, select “Options” and then “Show in Finder”. (If you can’t find the Safari shortcut on Dock, you can go to your “Applications” folder and find it there).
In the application window, right click on the Safari icon and click “Get Info”.
In the pop up menu, look for a checkbox named “Open in 32-bit mode” and check it. (If you can’t find it, you can click the “General” tab section to expand it.)
Quit and reopen Safari.