I found that the error message is misleading. After closing and launching MIPAV again, all the plugins appear on Windows 10. However, the plugins, JIST-CRUISE and others, are still not properly installed on Mac (Yosemite). As recommended elsewhere, I copied all the plugins directly into the 'plugins' folder under /mipav/ then the plugins appears but they don't appear right. It appears as file name, e.g., JIST-CRUISE-2014Dec12-03-37PM.jar.