As most Mac owners know by now they have dropped support for Java in Mac version 10.7.3 (Lion) or higher. Any new OS updates installed on your Mac will remove the java plugin that use to be on your system. Without the plugin you will be unable to run the javauploader of PhotoStore in your browser. To use the javauploader you will need to download the newest java plugin. Once this plugin is installed you will have reboot your entire computer. It may not work unless you reboot completely. Once rebooted then you will be able to use the javauploader in your photostore.
View this page from Java for more help in getting java working on your Mac: